Re: Port-A-Peater M100A Documentation
I think that was the on in a older 73 mag I think. I found on for what I have that way. Have to remember where it is.The ID'er was diode in the article, and on the factory version it is a prom.
Could be wrong, just rememebr the picture. I'll check here soon.
73
Mike - N7ZEF
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On Sun, 24 Jan 2021 12:54:46 -0700, Kevin Custer <kuggie@...> wrote: Gale,
A friend of mine had one of these early "repeater controllers" that was intended to take two mobile radios (of that era) and make a portable repeater for emergency use. As I recall, it's a plastic / metal case half the size of a shoe box that has connectors and knobs to set hang time and so on. I don't remember if it was VOX based or actually logic, but I remember it was constructed fairly well - considering the time. I don't remember it having a IDer.
Kevin
On 1/24/2021 2:44 PM, Gale Sorum wrote:
I'm looking for a copy of the documentation that came with a device called Port-A-Peater, built by a company called W-S Engineering located in Pine Hill, NJ. A quality control tag on the inside of the unit indicates it was built/tested on 11 Nov 1982. Unit I have appears to be NOS and in perfect mechanical condition. Google did not help in this case!
--
Using Opera's mail client:
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Re: Help identifying external interference source to our repeater
Wayne,
This was my?initial thought?as well but aside from a device drawing significant power in a repetitive pattern as observed I am not sure how this could be the case.? Another possibility, though I doubt it would be that strong, would be it could be wide-band PIM caused by interaction between?a nearby high-power transmitter and one or more metallic objects.? The testing I described should help narrow it down if possible - and yes an in-line attenuator, preferably variable, would be helpful in narrowing down the source whether testing?with?a receiver or a spectrum analyzer.
Thanks,
Dan Woodie, CETsr KC8ZUM
On Sun, Jan 24, 2021 at 7:01 PM wa5luy < wa5luy@...> wrote: It sounds just like a good old power line arc. I doubt it is more than a couple of miles away.?
It could be a tree limb touching the primary. Most likely it'd a defective bell or mushroom insulator. As someone has stated use an attenuator to reduce the signal to a point you can get a good reading in the direction. This is not recommended but a light tap on the pole where the problem is will generally reveal a lot of noise. The power company is responsible for fixing what is called "unintentional radiators " but I have found locating them generally falls on whoever is having the problem.? Also the degree of resolution varies greatly with the power company.
Good luck and keep us informed.
Wayne? WA5LUY
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Re: Port-A-Peater M100A Documentation
I am fairly certain (85%) I have said documents.?
I used to have one of those boards. They were advertised in one of the Ham rags back then, with some basic info and diagrams.?
I bought one of their "defective" boards for dirt cheap - before they went bust. It was merely a diode inserted backwards.?
I am in the hospital currently, I can look for it when I get home. It will be a few days or so before I can walk and such, to search. So... Have patience. I may not get out of here until Tuesday to start with, assuming a procedure goes well tomorrow.?
Feel free to contact me directly from here.?
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Re: Help identifying external interference source to our repeater
It sounds just like a good old power line arc. I doubt it is more than a couple of miles away.?
It could be a tree limb touching the primary. Most likely it'd a defective bell or mushroom insulator. As someone has stated use an attenuator to reduce the signal to a point you can get a good reading in the direction. This is not recommended but a light tap on the pole where the problem is will generally reveal a lot of noise. The power company is responsible for fixing what is called "unintentional radiators " but I have found locating them generally falls on whoever is having the problem.? Also the degree of resolution varies greatly with the power company.
Good luck and keep us informed.
Wayne? WA5LUY
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
I'm assuming the purpose built box is built for a higher duty cycle... vs mobile rig never intended for a high duty cycle re-purposed into a repeater.? ? Now, that being said... Once you open up some of those purpose built repeater boxes, what you find inside is two mobile radios... So perhaps it's a lot of sales hype more than anything.
It seems many individuals and groups when they want to put up a repeater opt to just buy a sometimes expensive box like a quantar, msf5000, msr2000, ge, kenwood, virtex, icom, etc and call it a day. Others will simply take 2 mobiles, tie them to a controller and call it a repeater (I¡¯m leaving out the duplexer and antenna, etc for simplicity assuming they are equal in both cases. What does one get for going the commercial box route vs the 2 transceiver route with a controller Tying them together?
Eric
Af6ep?
Sent using SMTP.
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Re: Port-A-Peater M100A Documentation
I found these 2 Porta-Peater Instant Repeater ads from 73 Magazine. Spent an hour searching with?no success finding the manual.
Original company?W-S Engineering PO BOX 58 PINE HILL NJ 08021 Phone 201-852-0269?
No luck finding any other information. There was an article?in the April 1997 QST page.
Tony N2MFT
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
Skyler Fennell asked:
Would anybody happen to have a figure here:
What is the typical natural environmental noise floor ( for standard 5KHz deviation FM bandwidth) for the 2 meter band vertically polarized 3dBi dipole antenna?
Assuming:
NO man made noise ( no powerlines nearby, no other electronics )
Room temperature: 75 degrees
VHF 2 meter band is used
Sunny day with no crazy storm weather
_________________________
Environmental noise is a complicated issue. ?
You can't rule out man made noise because it is a principle component of environmental noise, even in rural areas.
Numerous studies have been done with the results summarized in general guidance based on LULC (Land Use Land Cover).? Expect more noise in urban areas, less in rural areas.
Environmental noise at radio sites is highly variable, cannot be accurately predicted, and must be assessed either directly or indirectly.
Environmental noise tends to diminish with increasing frequency. Degradation of receiver effective sensitivity at radio sites will almost always be present at VHF but is seldom an issue above 400 MHz although you must always check effective sensitivity of any system because there can be degradation due to noise from other sources at or in in proximity to the site.
When proposing VHF systems, in the past, Motorola used 12.6 dB above kTB for determining the initial coverage predictions with the recommendation to the customer that the actual noise be evaluated at each proposed site.
Takeaway?? Expect some degradation of your 2 meter repeater receiver pretty much anywhere your site is located.
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Re: Port-A-Peater M100A Documentation
According to their ad, it was VOX or COR.? The ad can be seen here:
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Re: Help identifying external interference source to our repeater
John,
On initial listening it sounded like it could be a power line issue causing an arc - but the more I listened you can clearly hear it is data of some type, possibly TDMA data or similar due to the "buzz" in AM Mode, with the regular and often similar signal? Observing this signal on a spectrum analyzer may help you narrow down the source as you are likely seeing an image/mix/harmonic from a data transmitter.? It could be any number of things - from a cell phone or cell site to wifi, smarthome devices, or utility smart metering.? We had a similar issue that went on for weeks a few years back that not only intermittently?caused interference on VHF but also drifted up and down the VHF band including into public safety spectrum.? I successfully located the source of that interference after a few weeks which was the transmitter for a J-Tech paging system - the same as those used in many restaurants - located in the same-day-surgery waiting room of a local hospital.? The transmitter had a defect that was causing it to emit a spur in the VHF band and for some reason that spur would slowly drift up and down in frequency over time.? The transmitter was set for anti-walk-away mode which transmits a data signal at regular intervals - and if someone walks out of range with one of the pagers it sets the pager off, decreasing the chance of someone taking a pager or missing a page.? Hospital security powered down the device which confirmed it was the source and tagged it out of service until it could be replaced/repaired.
If possible I would recommend that you observe the signal with a spectrum analyzer as this will likely help you pinpoint the center frequency of the interference source, which is likely a much higher level than what you are observing.? If the noise is broad-band this method will also confirm that.? Keep in mind the selectivity of the receiver you are utilizing in these videos is quite broad and as such the signal may be perceived to be broadband when it may not, in fact, be so.? Your input frequency is also extremely close to the upper band-edge of 2M so the chances of receiving interference from a device in the commercial/public safety range is elevated.? Another useful observation would be if you could capture the audio waveform so it can be visually compared to known modulation types.? This can be done using a service monitor oscilloscope mode or simply recording the audio and using an audio editing application to inspect the waveform.
Thanks,
Dan Woodie, CETsr KC8ZUM
On Sun, Jan 24, 2021 at 12:56 PM < john@...> wrote: Hello all. I'm hoping someone can help me track down a new source of noise we're hearing on the input to our local 2m repeater at 147.990MHz.
Here's a couple short videos of what it sounds like while driving around the area listening on the input of the repeater. I used AM mode to enhance the noise a bit, but it can be heard under the signal of our weaker FM users on the repeater.
A few of the characteristics:
- Started around Jan 1, 2021, and wasn't a problem before that
- Broadband, I can hear it from about 138MHz to about 150MHz from my QTH
- Strong - I can hear this clearly from 5 miles on north and west of the repeater
- Has a semi-random pattern of pulses, and pauses for nearly a minute sometimes (see video links above to hear the noise)
- Is either on or off - doesn't seem to fade up or down in strength
- I did a little foxhunting, and the noise doesn't seem to be coming from one particular source, but is directional
Some of the theories we have are a local cable TV system leaking, one of the 345KV power lines in the area, an electric fence, lighting/signage etc.
That noise sound familiar to anyone?
Thanks
? - John, N8CD
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
Yikes, take your audio response out to 5khz Bob? Maybe on a link where you are your own customer but in the mobile relay band I think you are pushing it. You guys have no guard band out there in socal left at all with 20 khz channel spacing. I would really
not recommend audio over 3.4khz and deviation not to exceed 4.5 khz. Some people say do not exceed 4khz. Some of the tighter current technology radios will close up on audio and/or deviation not much wider than that.
td
wb6mie?
What seems to be getting lost in this discussion is that everyone has a different perception of what makes a repeater "excellent", & as such may have a different set of priorities when evaluating the manufacturers.? For example, I don't
care how much TX power a repeater has or if it has an internal power supply since it's my preference to use external amplifiers & supplies.? OTOH size matters: I don't have the room for a MASTR II base station or Quantar.? However, RF performance is still
important.? Finally, the subject of audio quality has been touched upon.? There are many of us who believe system audio should not necessarily be limited to the traditional 300-3000 Hz bandwidth.? 25 kHz, or even 20 kHz channel spacing, affords the opportunity
to expand the upper limit to 4 or even 5 kHz, & since most ham transceivers don't brick-wall filter the TX audio at 3 kHz, the resulting repeat audio is quite pleasant to listen to as well as more understandable.? This last point combined with the unusually
high failure rate of Motorola Quantars in this area gives me a rather low opinion of that otherwise "excellent" repeater, so-called.
-Henry F. Potter
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
At 1/23/2021 09:20 PM, you wrote: David,
Just out of curiosity what other repeaters have you had experience with?? If the Kenwood is all you have worked with - or the only relatively modern repeater you have worked with - then you may not be seeing the full picture here. What seems to be getting lost in this discussion is that everyone has a different perception of what makes a repeater "excellent", & as such may have a different set of priorities when evaluating the manufacturers. For example, I don't care how much TX power a repeater has or if it has an internal power supply since it's my preference to use external amplifiers & supplies. OTOH size matters: I don't have the room for a MASTR II base station or Quantar. However, RF performance is still important. Finally, the subject of audio quality has been touched upon. There are many of us who believe system audio should not necessarily be limited to the traditional 300-3000 Hz bandwidth. 25 kHz, or even 20 kHz channel spacing, affords the opportunity to expand the upper limit to 4 or even 5 kHz, & since most ham transceivers don't brick-wall filter the TX audio at 3 kHz, the resulting repeat audio is quite pleasant to listen to as well as more understandable. This last point combined with the unusually high failure rate of Motorola Quantars in this area gives me a rather low opinion of that otherwise "excellent" repeater, so-called. -Henry F. Potter
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
Dan,
I knew a Motorola (or Harris) solution was probably going to be the result
of my query. L.M.A.O. I've heard your "sales pitch" before, having sat
through similar sales and engineering briefings, hearing the unbelievably
incredible benefits of very high end radios being pitched to government
agencies, who are preparing to part with $1M+ of tax payer money.
As I already said, like many on this list, I maintain a small fleet of
Kenwood TKR-750v2/850v2 repeaters. They just sit there and work, 24/7.
Every single day they stay keyed for hours, sometimes even 24 hours or
longer, CONTINUOUSLY. No power derating, no burned up 13.8V power
supplies, no unsoldered PA transistors. No detectable desense. Their
receivers can hear a gnat sneeze. They just work. Many have been installed
for a decade now. I'm really not sure how anything could "vastly
outperform" this level of capability? Well, bluntly put, it can't.
So, that's my polite answer to your "sales pitch style" skepticism about
Kenwood TKR reliability. I feel sure you must know this already. I also
feel sure you realize that even the BatWings have bad days, bringing parts
of the fancy, highly redundant systems down. I've watched Mot rep camped
out at sites, complete with Holy Water, sometimes for a week or longer,
trying to perform an exorcism on a major system problem. I've seen
portions of systems down for weeks or longer, "waiting on parts." Don't
get me started on problems during and after Hurricanes, when vendors and
resources are stretched way too thin.
Meanwhile, my little, inexpensive, maintainable, Kenwood repeaters,
stuffed in small tower-mounted cabinets, just keep on working. and
working. and working. and working. (do I really need to go on?)
And, they're cheap enough that I've got several complete spare systems
"sitting on the shelf."
BTW, I have hauled heavy 3' x 19" sub-chassis racks up and down tall TV
towers a few times in my life. That's not really my idea of fun.
Anyhow, this horse has been beat to death.
73, David KB4FXC
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On Sun, 24 Jan 2021, Dan Woodie wrote: David,
It depends on the capabilities you require (such as digital modes), power
level, source power (AC or DC), external interface requirements, and your
budget.
Of current production repeaters I would say the "Excellent" repeaters would
be the Motorola GTR8000 for P25/Analog and SLR5700/SLR8000 for DMR/Analog.
I do not have a lot of experience with other high-tier current-production
models at this time but I am sure some others such as the Harris Mastr 5
and others may be reasonable - I just haven't had an opportunity to
evaluate them. I do not have the current pricing on these but the SLR8000
and GTR8000 are likely $10K+ if purchased new.
The benefit of high-tier repeaters is that they are made with high-quality
components and have a very long service life. As such a used repeater such
as a Motorola Quantar, with many years of service life left and an
abundance of parts availability, are available at very affordable prices of
$100-1500 depending on configuration and band - and will vastly outperform
and outlast many lesser repeaters even if they are new.
Not every application calls for an "excellent" repeater and for these
applications where lower power, fewer interface options, and sometimes less
reliability are acceptable, the Kenwood, Spectra Engineering, or
Daniels/Codan repeaters are good options that will better fit many
budgets. I would avoid Yaesu, Bridgecom, Vertex, Tait, and Icom repeaters
due to the low performance and poor quality I have observed and measured
though even these can work acceptably at some sites in some applications.
My intent of posting in this thread was not to talk down products or
criticise the choices of group members and I apologize if it was
interpreted as such by some. My hope was to have technical conversation
about the properties of different grades of repeaters and the benefit of a
high quality purpose-built repeater over a pair of mobiles or a lower-grade
repeater which is often just 2 mobiles in a housing - the original topic of
this thread.
Thanks,
Dan Woodie, CETsr
KC8ZUM
On Sun, Jan 24, 2021 at 11:47 AM David McGough <kb4fxc@...> wrote:
Dan,
I do have an unanswered question: What repeaters are available for NEW
purchase, which you consider "excellent" conventional FM repeaters?? What
is the typical price point, if I wanted to buy one new, right now??
73, David KB4FXC
On Sun, 24 Jan 2021, Dan Woodie wrote:
David,
Just out of curiosity what other repeaters have you had experience with?
If the Kenwood is all you have worked with - or the only relatively modern
repeater you have worked with - then you may not be seeing the full picture
here. Spend some time with the repeaters I named and I suspect your view
may change a bit. Again, I never said the Kenwood repeaters are inferior -
they are good for their price point - but not excellent for the reasons I
stated. They serve the needs of many satisfactorily but would not be my
first choice by any means these days with what is available on the used and
new markets. A used Quantar will blow those out of the water when it comes
to reliability, flexibility, interface options, wildcard scripting, etc -
but it depends on your needs. The Kenwood repeaters also do not have a
built-in Wireline interface so that also limits them in some applications.
I would buy a Kenwood any day over a Bridgecom, Yaesu, Icom, or Tait
repeater. Another example of a very good repeater - but one with some of
the same limitations I mentioned with Kenwood - is the Spectra Engineering
MX800. They are bulletproof and perform very well - the 220 MHz ones
probably make the best 220 ham repeaters available - but they have nowhere
near the capabilities of the repeaters I mentioned. This doesn't make them
bad - just not "excellent".
Thanks,
Dan Woodie, CETsr
KC8ZUM
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
Most of us on this list are advanced to expert level in repeater design, installation, acceptance testing, performance verification, operation and site environmental considerations. Although you provide a good resource for review, most of us do not really require
rehashing of detailed procedures for quantifying duplex sensitivity.?
I read the subject line and have to wonder...did the original poster's question actually get answered? It seems like a fairly straightforward, basic level question that I actually answered on my own repeater network this morning.?
So let me give my answer to the original poster, if he is still awake...
It all depends on what you want. If you want to build a basic repeater out of a transmitter and receiver, then do it. After you add a controller to it and run it for a little while in various configurations you may understand the advantages of using a purpose-built
appliance style repeater.?
On the repeater network I am associated with, we are presently moving away from the homebuilt kludges built from pieces of 30 to 40 year old hardware and moving toward the SLR-5700 Motorola product. It's current technology, has no problems with continuous duty
transmit at its full 50 watt output and has a wide temperature range of operation. And it occupies one rack unit. In a time when we are paying for rack space by the inch, that is an important consideration. Yes, there is a lot of capability inside the box
that we are not using, but that's ok with me. It's still in there if we ever need it. It has a fully functional interface connector and gpios for integration with our network hardware. And it's new, covered by warranty in some cases. It's a far cry from old
junk box crap that is going into perhaps a tertiary life cycle.
Just my opinion, discussion on original topic invited.
td
wb6mie
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Skyler,
I would define RF desense as a decrease in effective receiver sensitivity caused by external noise sources,?measured through SINAD for Analog FM receivers and BER for digital receivers,?and can be caused by both environmental sources?
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Re: Help identifying external interference source to our repeater
Hi John,
I noticed you are centering in on the repeater's input.?? I doubt that's the strongest frequency (that would be like winning the reverse lottery).?? Look around elsewhere. ? and probably, you may see stronger signals down lower in frequency. ? The comment you just got about the windmills seem valid. ? They can generate a huge amount of static, and regular intervals depending on the wind speed.??
Anyway, as you dial down the band, you may get further clues with more signal.? Good luck!
And as previously stated, please keep us informed!
Andy WJ9J
On Sun, Jan 24, 2021 at 3:41 PM Frank Perkins < N6CES.r@...> wrote: Hi John, I listened to the audio and noticed a few things. Each pulse is fast rise/fast fall, 2 or 3 strengths, random, but in spread clusters. Almost like static discharge. Area of coverage suggests extreme high rf source, or something with a long radiation antenna. I would rule out electric fence, because those discharge controllers pulse at regular intervals. I would then suspect the high voltage power lines. An arc-over flash? would have an excellent antenna. Do you notice any change from dry to rainy day? I would hope in the car with the DF and drive the power line. Also, don't know where you live, but if around power generating windmill turbines, they build up a tremendous amount of static electricity on the blades. This is interesting. Keep us posted. Frank N6CES
On Sun, Jan 24, 2021, 10:08 AM K8TB < k8tb@...> wrote:
Whatever it is, you will be surprised.
You need to do a little more,
especially in the DF area. The good news, compared to a human
jammer, is that is is there all the time.
Can you hear it on a handheld on the
ground at the repeater site? If so, take some readings. (remember
to move sideways 10 feet, take? another reading to identify a
multipath reading.)
Can you hear it from a car mobile? If
so, even the simple X-Y grid driving can narrow it down.
A little social engineering. Is it
24/7, or does it comes at go at certain times?
Could be just about anything. I've DF'd
Micor paging transmitters on UHF that break loose. Never had one
on VHF, so far.
Two hours DF'ing will help.
Oh, you are now required to post back
to this group what you find! ::)
Tom K8TB
Hello all. I'm hoping someone can help me track down a new source
of noise we're hearing on the input to our local 2m repeater at
147.990MHz.
Here's a couple short videos of what it sounds like while driving
around the area listening on the input of the repeater. I used AM
mode to enhance the noise a bit, but it can be heard under the
signal of our weaker FM users on the repeater.
A few of the characteristics:
- Started around Jan 1, 2021, and wasn't a problem before that
- Broadband, I can hear it from about 138MHz to about 150MHz
from my QTH
- Strong - I can hear this clearly from 5 miles on north and
west of the repeater
- Has a semi-random pattern of pulses, and pauses for nearly a
minute sometimes (see video links above to hear the noise)
- Is either on or off - doesn't seem to fade up or down in
strength
- I did a little foxhunting, and the noise doesn't seem to be
coming from one particular source, but is directional
Some of the theories we have are a local cable TV system leaking,
one of the 345KV power lines in the area, an electric fence,
lighting/signage etc.
That noise sound familiar to anyone?
Thanks
? - John, N8CD
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Re: Help identifying external interference source to our repeater
Hi John, I listened to the audio and noticed a few things. Each pulse is fast rise/fast fall, 2 or 3 strengths, random, but in spread clusters. Almost like static discharge. Area of coverage suggests extreme high rf source, or something with a long radiation antenna. I would rule out electric fence, because those discharge controllers pulse at regular intervals. I would then suspect the high voltage power lines. An arc-over flash? would have an excellent antenna. Do you notice any change from dry to rainy day? I would hope in the car with the DF and drive the power line. Also, don't know where you live, but if around power generating windmill turbines, they build up a tremendous amount of static electricity on the blades. This is interesting. Keep us posted. Frank N6CES
On Sun, Jan 24, 2021, 10:08 AM K8TB < k8tb@...> wrote:
Whatever it is, you will be surprised.
You need to do a little more,
especially in the DF area. The good news, compared to a human
jammer, is that is is there all the time.
Can you hear it on a handheld on the
ground at the repeater site? If so, take some readings. (remember
to move sideways 10 feet, take? another reading to identify a
multipath reading.)
Can you hear it from a car mobile? If
so, even the simple X-Y grid driving can narrow it down.
A little social engineering. Is it
24/7, or does it comes at go at certain times?
Could be just about anything. I've DF'd
Micor paging transmitters on UHF that break loose. Never had one
on VHF, so far.
Two hours DF'ing will help.
Oh, you are now required to post back
to this group what you find! ::)
Tom K8TB
Hello all. I'm hoping someone can help me track down a new source
of noise we're hearing on the input to our local 2m repeater at
147.990MHz.
Here's a couple short videos of what it sounds like while driving
around the area listening on the input of the repeater. I used AM
mode to enhance the noise a bit, but it can be heard under the
signal of our weaker FM users on the repeater.
A few of the characteristics:
- Started around Jan 1, 2021, and wasn't a problem before that
- Broadband, I can hear it from about 138MHz to about 150MHz
from my QTH
- Strong - I can hear this clearly from 5 miles on north and
west of the repeater
- Has a semi-random pattern of pulses, and pauses for nearly a
minute sometimes (see video links above to hear the noise)
- Is either on or off - doesn't seem to fade up or down in
strength
- I did a little foxhunting, and the noise doesn't seem to be
coming from one particular source, but is directional
Some of the theories we have are a local cable TV system leaking,
one of the 345KV power lines in the area, an electric fence,
lighting/signage etc.
That noise sound familiar to anyone?
Thanks
? - John, N8CD
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
I would agree with that. Environmental?noise is almost always above top quality high performance receiver noise floors, so therefore your definition of desense would be occurring, even on a receive only site.
Would anybody happen to have a figure here:
What is the typical natural enviromental noise floor ( for standard 5KHz deviation FM bandwidth) for the 2 meter band vertically polarized 3dBi dipole antenna?
Assuming:? NO man made noise ( no powerlines nearby, no other electronics ) Room temperature: 75 degrees VHF 2 meter band is used Sunny day with no crazy storm weather
On Sun, Jan 24, 2021 at 12:53 PM Dan Woodie < kc8zum@...> wrote: Skyler,
I would define RF desense as a decrease in effective receiver sensitivity caused by external noise sources,?measured through SINAD for Analog FM receivers and BER for digital receivers,?and can be caused by both environmental sources as well as co-located or nearby transmitters.? If the definition was as has been stated and required a transmitter then receivers without co-located transmitters would never have any measurable desense - which is simply not the case.? It may be possible but extremely rare to have no measurable transmit desense in a system?with high levels of isolation (>100 dB).? While good filtering can significantly reduce transmit desense it cannot reduce on-frequency environmental/site noise and the associated desense.? Proper transmit filtering (harmonic filters, circulators, band-pass, etc) can reduce wide-band site noise and mix products generated by other devices at a site which can result in increased environmental/site desense.? If all transmitters used such filtering this kind of noise and desense would not be nearly as pervasive?as it is today.? Cost, space requirements, and insertion loss are the down-sides of such filtering and are the primary reasons many transmitters do not use some or all of these.
Below is a link to an interesting article from a respected industry publication that discusses much of what I have presented (but is not the source of what I have presented - as I just found this article minutes ago).? It does not go into too much detail of the impact of environmental/site desense but describes similar measurement procedures and many other?factors that?should be considered.
Another related topic is noise floor which as you mentioned can be impacted by thermal parameters if the receiving device is the source of the elevated noise floor.??
From Wikipedia (link below):?In radio communication and electronics, this may include?,?,??as well as??from distant thunderstorms and similar and any other unwanted man-made signals, sometimes referred to as incidental noise. If the dominant noise is generated within the measuring equipment (for example by a receiver with a poor?) then this is an example of an instrumentation noise floor, as opposed to a physical noise floor. These terms are not always clearly defined, and are sometimes confused.
The impact of the noise floor is the cause of environmental/site desense.? Internally-generated thermal noise in a receiver is not generally considered desense when the device is operated within the manufacturer-specified temperature range as it is not something that is generally easily or reasonably controlled and has little impact in most cases.? This factor is accounted for in measured chassis sensitivity so is included in the baseline measurements.
Thanks,
Dan Woodie, CETsr KC8ZUM
On Sun, Jan 24, 2021 at 11:36 AM Dan Woodie < kc8zum@...> wrote: Skyler,
I see now where the disconnect is between your interpretation of desense and what I presented.
On my previous post before that I mentioned both environmental / site noise and transmitter noise. I was corrected by David McGough that desense is only defined as degradation due to your transmitter, not site noise, so I¡¯m not sure which one is correct.?
There are two distinct types of desense - Environmental/Site Desense and Transmit Desense.? A good quality repeater that is properly configured with good filtering?at a reasonably quiet site may not have much of either - to the point where they are not a factor - but my point was there is still some level of desense whether it impacts operation or not.
As per considering both site noise and transmitter interference, I would still believe that in a perfectly quiet site, your receiver noise floor of a typical 0.15uV sensitivity receiver is above the background noise, but there is a point where KBt noise (boltsmans constant) comes into play just by the environment having temperature, so I guess assuming your receiver is more sensitive than background noise generated at room temperature, probably by being super cooled, you will always be limited by the noise temperature of the environment.?
On Sun, Jan 24, 2021 at 8:36 AM Dan Woodie < kc8zum@...> wrote: Kevin,
I can assure you that all of my comments regarding desense are based on scientific data and my extensive training.? I would be happy to walk you through how to validate this if you would like.? If you can prove my statements incorrect I would be happy to post a retraction of my statements on the matter.? In many cases the level of desense I am referring to may not have any perceivable impact on operations but it does not mean it does not exist and is not measurable.? At some sites it is only a fraction of a dB.
Desense is not a logarithmic function of how well your equipment is setup?where incremental?improvements in the setup will cause?incremental?improvements of less desense. It is either there or not, and just a game of how many dB's your isolation is,?and rarely?would you have, say, 1/100 of a dB of desense. You either have enough isolation or you don't. If the isolation is enough, the desense is not there.?
On all repeaters I have setup, I put as weak of a signal that I can, measure the SINAD with TX OFF, and then measure the SINAD with TX ON, and observe any fractional changes. If it's setup right, there's no change. No popping on the RX when you key the TX, and nothing when you wiggle all the coax around.?
From David McGough Desense and site noise floor are 2 different things:??
Yes, my bad, and I was putting those two in the same category.
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Re: Port-A-Peater M100A Documentation
Gale,
A friend of mine had one of these early "repeater controllers" that was intended to take two mobile radios (of that era) and make a portable repeater for emergency use.? As I recall, it's a plastic / metal case half the size of a shoe box that has connectors and knobs to set hang time and so on.? I don't remember if it was VOX based or actually logic, but I remember it was constructed fairly well - considering the time.? I don't remember it having a IDer.
Kevin
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On 1/24/2021 2:44 PM, Gale Sorum wrote: I'm looking for a copy of the documentation that came with a device called Port-A-Peater, built by a company called W-S Engineering located in Pine Hill, NJ.? A quality control tag on the inside of the unit indicates it was built/tested on 11 Nov 1982. Unit I have appears to be NOS and in perfect mechanical condition. Google did not help in this case!
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
On 1/24/2021 1:51 PM, Dan Woodie wrote: Kevin,
I appreciate your input and view.? I apologize if my posts did not properly convey what I was trying to in an appropriate manner. I accept your apology and look forward to properly educating by using facts backed up by solid engineering.? We all have opinions, but not many of us have the ability to write in a manner that's educational and not condescending.? I never felt you were combing my fur backwards on purpose, because if I did you wouldn't be here any more. I'll complement you on your desire to debate tough subjects to tough subjects (members), after all, it's National Complement Day! Kevin
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Port-A-Peater M100A Documentation
I'm looking for a copy of the documentation that came with a device called Port-A-Peater, built by a company called W-S Engineering located in Pine Hill, NJ.? A quality control tag on the inside of the unit indicates it was built/tested on 11 Nov 1982. Unit I have appears to be NOS and in perfect mechanical condition. Google did not help in this case!
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Re: Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together?
I started this thread and as a relative noob in this area I have appreciated the discourse as to grades of repeaters and some of the issues that come up more often in some than others. Different people will have different opinions on the matter and even a different outlook sometimes as to what facts matter performance wise and which do not. ?Woodie¡¯s comments have been quite valuable to me as have the comments of the rest of the group. I do not find them condescending at all and they do seem to be on the mark. Often the point between good (enough) and excellent (the knee in the rice performance curve where the line goes asymptotic) is worth looking at. Also sometimes the used market is worth looking at, especially when it outperforms new stuff offered at its current price point. If I can buy a quantar of msf5k for the same or less than a new yaecomwood radio with plenty of parts and service info still available I¡¯m probably going to look hard at which box has more of the features I need and offers the best performance and reliability for the price I can afford. ?Thank you all for your comments. I look forward to reading all your continuing comments on this topic.?
Eric Af6ep?
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On Jan 24, 2021, at 10:01 AM, Dino Darling <dino@...> wrote:
?
Wow...I don't think I've ever seen a more condensending person in my life. Woodie would already be gone if this was my group. I own the ham-amplifiers group here on groups.io and it is the least moderated group I've ever seen. After the people there were done
chewing him up and spitting him out he'd be kicked to the curb.
Now this is just my opinion based on my extensive scientific study of human behavior...or the lack of it.
Dino - KX6D
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wa5luy
John Tetreault (WA1OKB)
Kevin Custer