Re: Clamp meter mistake -- watch for a balanced meter movement if analog
Showing my ignorance I did not know a "balance" meter existed.
--
Regards, Karl Shoemaker
To contact me, please visit SRG's web site at?
for the current email address.
-
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Does anyone need anything from this before it goes away?
Cleaning out.
Will
Contact radio5000 (at) aol (dot) com
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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?
Very true on the TX phase noise point. I¡¯ve fought with a user at 451MHz using an icom mobile with no bandpass or isolator. They were a few MHz away and desensing ? us bad.?
It turns out my desense was from their phase noise, luckily they were not mixing. Small bandpass cavities had no help, we needed a realllly narrow skirts fat guy to get their phase noise off our input. Luckily BNSF was nice enough to let us put a bpf on their radio but not nice enough to pay for it.?
Most bandpass cavities will not solve phase noise on TX within a few MHz because they usually have very little loss +- a few MHz, 10-15dB is sometimes not enough.?
A notch filter for our TX on their radio would have been the easiest way, but there were multiple hams being degraded by their phase noise so we needed to filter everything out below 450MHz?
On Sun, Jan 17, 2021 at 9:47 AM peter oesterle < phoesterle@...> wrote:
Also,?? mobiles? are designed? for freq agility,? therefore a?? wider bandwidth.
The older? GE MII and? MICOR? and? MSF5000 ,? were tuned for? fixed freq operation? as a repeater.
Narrow band???? operation.
Not 138 to 174? as most mobiles? are today.
The eary ICOM? 2m mobiles? had? 4 pole helical filters in them.?? Examples? are? IC22A???? IC25.
They were? pretty selective,? keeping out? non 2m? RF.
GE MII and? MICORs?? also had? great? helical front ends.
Want better? RX , add a? helical filter!?
It's simple !
Do not forget? the issue? of? phase npise on? a? TX? or? the? RX? local oscillators.
GE MII and? MOT?? are usually?? a? lot cleaner.
?I? have? experienced? RX? desense where? Yaesu? radios?? transmitted? ,? vs??? MOT?? mobiles? TXing on the? same freq.] with similar power levels.
You get what you pay for!?
I see no problem with using two mobiles and I do it all the time and the performance is identical to the fancy repeaters.?
Sensitivity: I don¡¯t see much difference in RX sensitivity between most mobiles and purpose built but if need be I can add a pre-amp.?
Selectivity: This is where many mobiles are lacking. BpBr Duplexers seem to give me enough selectivity for an average mobile but if it¡¯s really bad, I will add another pre selector.?
Keep in mind the average Motorola mobile is much more selective than the average Yaesu repeater.?
Duty Cycle: another big issue, you will blow up your mobile if you talk at full power on full duty. I have never had an issue full duty half power with a nice fan on Motorola mobiles. In addition I have often used repeater grade PA¡¯s from old
crystal controlled repeaters like the GE mastr because crystals are more expensive than mobiles.?
Standardization: this is my weak point. I have different configuration of mobiles all over the state of Colorado and if one fails it¡¯s going to have a completely different construction than another. If every repeater was a standard it will save
me time in the future. Hopefully I have all my documentation.?
Intermod: NEVER interface a mobile directly to an antenna at a high RF site, but I think the same would go with repeaters so I don¡¯t think there is any reason a mobile would be worse, a PA is a PA and it¡¯s gonna mix if there¡¯s enough RF coming
back. But some PA¡¯s have built in circulators which I guess would never happen on a mobile.?
I have never had a site owner care about mobiles at a site vs ¡°professional¡± repeaters and I have been able to make pretty nice looking mobile installs and I have seen pretty ugly looking ¡°real¡± repeater installs.?
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Re: Looking for a Motorola Quantar
Andrew,
You may want to specify which range you require.? VHF Range 2 Quantars (150-174) are much more common than VHF Range 1 Quantars (136-150).? While the Range 1 Quantar will do the whole 2M range they are difficult to find and often quite expensive whereas Range 2 are more common and less expensive but can generally only stretch down to around 146.2 - so if you are on the high end of the band you can probably get away with Range 2.? Also if you plan to run P25 or Mixed-mode with linking like P25NX or Quantar Bridge you probably will want one with a V.24 card.? You may also want to specify if you want 25W or 125W and AC or DC power supply.? There is also a variant of Quantar available that is much higher power known as a Quantro.? These are generally 325W units but can be turned down to 200-250W.? I have set a couple of these up for clubs in the past.? Duplexer power handling and isolation is a consideration with these but they can be reasonably priced from my experience.?
Thanks,
Dan Woodie, CETsr KC8ZUM
Since its now official that Hamvention is cancelled this year, I have to go online to start my hunt for a repeater. I'm looking for a VHF Motorola Quantar for a new repeater project. If anyone in the group has one in good working condition, feel free to email me.
andrew.grimm016 'at'
73
Andrew - K8ATG
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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?
Also,?? mobiles? are designed? for freq agility,? therefore a?? wider bandwidth.
The older? GE MII and? MICOR? and? MSF5000 ,? were tuned for? fixed freq operation? as a repeater.
Narrow band???? operation.
Not 138 to 174? as most mobiles? are today.
The eary ICOM? 2m mobiles? had? 4 pole helical filters in them.?? Examples? are? IC22A???? IC25.
They were? pretty selective,? keeping out? non 2m? RF.
GE MII and? MICORs?? also had? great? helical front ends.
Want better? RX , add a? helical filter!?
It's simple !
toggle quoted message
Show quoted text
Do not forget? the issue? of? phase npise on? a? TX? or? the? RX? local oscillators.
GE MII and? MOT?? are usually?? a? lot cleaner.
?I? have? experienced? RX? desense where? Yaesu? radios?? transmitted? ,? vs??? MOT?? mobiles? TXing on the? same freq.] with similar power levels.
You get what you pay for!?
I see no problem with using two mobiles and I do it all the time and the performance is identical to the fancy repeaters.?
Sensitivity: I don¡¯t see much difference in RX sensitivity between most mobiles and purpose built but if need be I can add a pre-amp.?
Selectivity: This is where many mobiles are lacking. BpBr Duplexers seem to give me enough selectivity for an average mobile but if it¡¯s really bad, I will add another pre selector.?
Keep in mind the average Motorola mobile is much more selective than the average Yaesu repeater.?
Duty Cycle: another big issue, you will blow up your mobile if you talk at full power on full duty. I have never had an issue full duty half power with a nice fan on Motorola mobiles. In addition I have often used repeater grade PA¡¯s from old
crystal controlled repeaters like the GE mastr because crystals are more expensive than mobiles.?
Standardization: this is my weak point. I have different configuration of mobiles all over the state of Colorado and if one fails it¡¯s going to have a completely different construction than another. If every repeater was a standard it will save
me time in the future. Hopefully I have all my documentation.?
Intermod: NEVER interface a mobile directly to an antenna at a high RF site, but I think the same would go with repeaters so I don¡¯t think there is any reason a mobile would be worse, a PA is a PA and it¡¯s gonna mix if there¡¯s enough RF coming
back. But some PA¡¯s have built in circulators which I guess would never happen on a mobile.?
I have never had a site owner care about mobiles at a site vs ¡°professional¡± repeaters and I have been able to make pretty nice looking mobile installs and I have seen pretty ugly looking ¡°real¡± repeater installs.?
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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?
Do not forget? the issue? of? phase npise on? a? TX? or? the? RX? local oscillators.
GE MII and? MOT?? are usually?? a? lot cleaner.
?I? have? experienced? RX? desense where? Yaesu? radios?? transmitted? ,? vs??? MOT?? mobiles? TXing on the? same freq.] with similar power levels.
You get what you pay for!?
toggle quoted message
Show quoted text
I see no problem with using two mobiles and I do it all the time and the performance is identical to the fancy repeaters.?
Sensitivity: I don¡¯t see much difference in RX sensitivity between most mobiles and purpose built but if need be I can add a pre-amp.?
Selectivity: This is where many mobiles are lacking. BpBr Duplexers seem to give me enough selectivity for an average mobile but if it¡¯s really bad, I will add another pre selector.?
Keep in mind the average Motorola mobile is much more selective than the average Yaesu repeater.?
Duty Cycle: another big issue, you will blow up your mobile if you talk at full power on full duty. I have never had an issue full duty half power with a nice fan on Motorola mobiles. In addition I have often used repeater grade PA¡¯s from old
crystal controlled repeaters like the GE mastr because crystals are more expensive than mobiles.?
Standardization: this is my weak point. I have different configuration of mobiles all over the state of Colorado and if one fails it¡¯s going to have a completely different construction than another. If every repeater was a standard it will save
me time in the future. Hopefully I have all my documentation.?
Intermod: NEVER interface a mobile directly to an antenna at a high RF site, but I think the same would go with repeaters so I don¡¯t think there is any reason a mobile would be worse, a PA is a PA and it¡¯s gonna mix if there¡¯s enough RF coming
back. But some PA¡¯s have built in circulators which I guess would never happen on a mobile.?
I have never had a site owner care about mobiles at a site vs ¡°professional¡± repeaters and I have been able to make pretty nice looking mobile installs and I have seen pretty ugly looking ¡°real¡± repeater installs.?
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Re: Motorola XPR8300 repeater, no USB comms
I ran into what I think is the same issue a couple years ago. I had picked up an XPR8300 that CPS absolutely could not see. I bought a replacement network interface thinking it was a hardware problem; it was not.
You need to find old CPS to be able to interact with it. Motorola apparently quietly drops support for old firmware in some releases. You can then upgrade it to something that newer CPS will see. IIRC, the older builds are on the MOL website too.
I think the unmentionable tool that rhymes with Crab was able to see it in all cases, which helped determine that the repeater was OK, just too old for modern CPS to see.
Hi guys.? I have an issue with USB comms to an early model XPR8300 repeater.? ?It's has been extremely stubborn.? ?I've tried everything, different PC's, different cables, both CPS16, and CPS2,? tried the rear USB on the TX and RX bricks individually, tried as USB-2 hub, still NOTHING.? No USB comms on all 3 connections.? Just keep getting comm errors, no USB problems like this with my other trbo radios and the same programming gear.? ??
?
The thing that's DIFFERENT on this repeater vs. my others is ver. 1.04.01.???My others that are Ver. 1.06.20 have no problems with USB ports.? ?Obviously, I can't even upgrade the firmware if? I can't talk to it.? Anyone seen this?? Thanks so much in advance!
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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 see no problem with using two mobiles and I do it all the time and the performance is identical to the fancy repeaters.?
Sensitivity: I don¡¯t see much difference in RX sensitivity between most mobiles and purpose built but if need be I can add a pre-amp.?
Selectivity: This is where many mobiles are lacking. BpBr Duplexers seem to give me enough selectivity for an average mobile but if it¡¯s really bad, I will add another pre selector.?
Keep in mind the average Motorola mobile is much more selective than the average Yaesu repeater.?
Duty Cycle: another big issue, you will blow up your mobile if you talk at full power on full duty. I have never had an issue full duty half power with a nice fan on Motorola mobiles. In addition I have often used repeater grade PA¡¯s from old crystal controlled repeaters like the GE mastr because crystals are more expensive than mobiles.?
Standardization: this is my weak point. I have different configuration of mobiles all over the state of Colorado and if one fails it¡¯s going to have a completely different construction than another. If every repeater was a standard it will save me time in the future. Hopefully I have all my documentation.?
Intermod: NEVER interface a mobile directly to an antenna at a high RF site, but I think the same would go with repeaters so I don¡¯t think there is any reason a mobile would be worse, a PA is a PA and it¡¯s gonna mix if there¡¯s enough RF coming back. But some PA¡¯s have built in circulators which I guess would never happen on a mobile.?
I have never had a site owner care about mobiles at a site vs ¡°professional¡± repeaters and I have been able to make pretty nice looking mobile installs and I have seen pretty ugly looking ¡°real¡± repeater installs.?
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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?
There have been a lot of comments on this subject, unless I missed something, no one has said anything about NOT using amateur mobile radios to make a repeater. This would include Fusion.
Often times an external controller may be required on a commercially made repeater as well. Such as for the identifier, if linking is used, and most importantly often times for required remote control. The number of messages that have shown up on this list from people talking about the time or difficulty to get to their repeater to be able to turn off the transmitter. That is what the required remote control is about.
Mick - W7CAT
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----- Original Message ----- From: Eric Fort To: [email protected]Sent: Saturday, January 16, 2021 07:22:23 PM Subject: [repeater-builder] Why use a purpose built repeater box as a repeater rather than a transmitter, receiver, and controller tied (lashed) together? 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.
-- Untitled Document
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Re: TPRD-1554 Troubleshooting
As received, each cavity was tested separately using a DSA815 spectrum analyzer with tracking generator and a high quality 50 ohm load.
The insertion loss of each was 0.7 dB and the notch depth was at least -35 dB. 35 dB notch depth is a bit low with loops set for 0.7 dB IL. Touching the trimmer with the insulated tuning tool caused the notch to flatten out at about the 15 dB level. That indicates the capacitor is shorting out. Piston trimmer caps are rather fragile beasts. There are several concentric plates in the piston and stator. The slightest eccentricity will cause them to short. It is almost guaranteed to need to be replaced. You can unscrew the rotor all the way, and, using a magnifying glass, look closely at the plates on both sides. I bet you'll see either a slight distortion, pit, or something that will be the reason for it shorting out. I'm also curious about the cable lengths. The inter cavity cables are the same length for both the transmit
and receive branches. They are RG-214 precisely 12.125 inches long measured tip to tip.
I would have expected the lengths to have been slightly different because of the different frequencies,
but maybe at a 600 kHz split the difference is negligible since it's only about one tenth of an inch or less. Comments? Between adjacent cavities - cable lengths would not vary because the frequencies are so close. Between cavities and the antenna tee, the correct length is a function of Z of the opposing cavity at its notch frequency (i.e. at the opposing side's pass frequency), with the goal of rotating that Z to be back at the T to make it appear as an open circuit. Many times, but not always, the lengths to the tee end up being equal. The other length I'm curious about is what Telewave refers to as the phasing cables. These are the cables
between the cavities and the antenna TEE. Their documentation states these cables should be
1/2 wavelength at the reject frequency. Telewave is decidely wrong. The lengths of the RG-214 cables on this duplexer are both the
same and only 13.5 inches long tip to tip.
These seem way short since 1/2 wave cables at these frequencies is 26 inches and change. Comments? Optimized cable lengths for the ham band: Between cavities: 12.125" RG214 tip to tip Tee to first cavity on each side: 12.625" RG214 tip to tip The latter works out to about 84 degrees...nowhere near 180 degrees. --- Jeff WN3A -- This email has been checked for viruses by Avast antivirus software.
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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?
For ham repeaters usually the ones that put them together out of parts know how to work on them and will take time to fine tune the repeater.? The ones that just set the commercial box down are not that well versed in repair work.
The 'home built' repeaters are often set up in modules or separate transceivers that can be removed and replaced with a? spare unit.? The commercial units will be down for a while, especially if there is no back up repeater that can be put in place.
It was mentioned about how the commercial repeaters were so well designed.? Some are not and are just the mobile units set for reduced power and put into nice looking boxes.
Ralph ku4pt
On Saturday, January 16, 2021, 09:59:59 PM EST, Eric Fort <eric.fort.listmail@...> wrote:
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
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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?
The R1225 is rated at 25 watts continuous.? That's not 25 watts out of the duplexer either.?? That's where a lot of people make a mistake.? Run them at 25 watts out of the radio (or better yet, 20) and they will last for years and years. ? If you need more power, get the 10W version and run through a can to an external PA and they run 10W no issue for hours. ? But still use a fan!
Andy WJ9J? ?
On 1/16/2021 10:53 PM, TGundo 2003 via wrote:
> To retort:
>
> Many, if not most, current "factory" repeaters today are nothing more
> than 2 mobiles in a box
Not always true.? For example, the Motorola R1225 repeater appears to be
a mobile, but the heat sink is much larger than on the regular M1225 mobile.
Joe
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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 1/17/2021 8:31 AM, fire22pa via groups.io wrote: The r1225 is still not a 100% duty cycle machine. They have a week spot at full power? the solder melts on the final and causes a failure we have on in service but cut back to 20 watts. True, but I have had success at running them at 22 watts.? have a couple of them here that I use for backup replacement repeaters while doing repairs. The last time I used it was on a VHF ham repeater that has a weekly net that sometimes runs 30-40 minutes. The R1225 survived well, but the fan MUST be running. I have another VHF one on the air at a club repeater site for a couple of years now. The old Spectrum Communications SCR-77 repeater at this site finally gave up the ghost. The R1225 repeater is definitely not my first choice as a full-time repeater, but they do work if you keep them in a reasonably heat friendly environment. Not a good choice for a heavily populated commercial site. 73, Joe, K1ike
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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?
The r1225 is still not a 100% duty cycle machine. They have a week spot at full power? the solder melts on the final and causes a failure we have on in service but cut back to 20 watts.
On Sun, Jan 17, 2021 at 8:25, Joe <k1ike_mail@...> wrote: On 1/16/2021 10:53 PM, TGundo 2003 via groups.io wrote:
> To retort:
>
> Many, if not most, current "factory" repeaters today are nothing more
> than 2 mobiles in a box
Not always true.? For example, the Motorola R1225 repeater appears to be
a mobile, but the heat sink is much larger than on the regular M1225 mobile.
Joe
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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 1/16/2021 10:53 PM, TGundo 2003 via groups.io wrote: To retort:
Many, if not most, current "factory" repeaters today are nothing more than 2 mobiles in a box Not always true.? For example, the Motorola R1225 repeater appears to be a mobile, but the heat sink is much larger than on the regular M1225 mobile. Joe
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Motorola XPR8300 repeater, no USB comms
Hi guys.? I have an issue with USB comms to an early model XPR8300 repeater.? ?It's has been extremely stubborn.? ?I've tried everything, different PC's, different cables, both CPS16, and CPS2,? tried the rear USB on the TX and RX bricks individually, tried as USB-2 hub, still NOTHING.? No USB comms on all 3 connections.? Just keep getting comm errors, no USB problems like this with my other trbo radios and the same programming gear.? ??
?
The thing that's DIFFERENT on this repeater vs. my others is ver. 1.04.01.???My others that are Ver. 1.06.20 have no problems with USB ports.? ?Obviously, I can't even upgrade the firmware if? I can't talk to it.? Anyone seen this?? Thanks so much in advance!
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Re: TPRD-1554 Troubleshooting
Yep bad cap. I have had that happen a couple times. Also the BPBR coupling loops for the VHF telewave cavities for 2M are a tad longer than those use in the commercial region. There was a write up awhile back out of VK land that covered this.?
I have found the 4 cavity filter lacks enough isolation. I suggest adding two 5¡± bandpass cavities on the RX leg. I found this to work very well.?
Last year I built a 5 channel TX combiner 1-10¡± band pass and 2 or 3 BPBR cavities per channel. RX side was 2 5¡± BPBR and 2 5¡± Bandpass. Everything had >90 dB of isolation in just the filters. The. Another 40 dB of isolation. Between the 2 two bay stacked VHF Dipoles. All the systems really work. No desense and the receivers have excellent Bandpass isolation.?
My .02.?
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On Jan 16, 2021, at 5:45 PM, Jack Mcelyea/n4jem via groups.io <n4jem@...> wrote:
?
Any time a cap jumps around it is bad and the green junk is a sure sign of water  On Saturday, January 16, 2021, 8:20 PM, Eric Grabowski via groups.io <ejgrabowski@...> wrote: I'm working on this VHF duplexer our club acquired from another Ham. He doesn't know any of the history before he received it, so I don't know if this was factory ordered for the 2 meter band or if it was originally built for a high band commercial application and retuned somewhere along the line. Since I've never worked on any Telewave cavities, I'm hoping for a little help from those of you who have.
As received, each cavity was tested separately using a DSA815 spectrum analyzer with tracking generator and a high quality 50 ohm load. The insertion loss of each was 0.7 dB and the notch depth was at least -35 dB.
The only problem encountered was while tweaking the notch capacitor on the cavity closest to the antenna TEE in the receive branch. Touching the trimmer with the insulated tuning tool caused the notch to flatten out at about the 15 dB level. Turning the capacitor cause the trace to jump around wildly. Attempting to tweak it a little then removing the tool trying to luck out and hit the notch frequency was a waste of time. The tuning definitely appeared to be nonlinear.
I pulled the loop and it all seems to be intact. The solder joints look shiny and solid. So the question is: Does this indicate a bad capacitor?
The only suspicious area is the top of the plate which has a light layer of green residue, which is probably from the humid environment it lived in. By the way, the plates on all the other cavities have the same amount of green residue and they tune up fine. So might it be possible that this particular capacitor is not making a good physical ground connection to the plate? I should add that all of the capacitors had their protective caps installed so I don't believe any dust particles are to blame.?
I'm also curious about the cable lengths. The inter cavity cables are the same length for both the transmit and receive branches. They are RG-214 precisely 12.125 inches long measured tip to tip. I would have expected the lengths to have been slightly different because of the different frequencies, but maybe at a 600 kHz split the difference is negligible since it's only about one tenth of an inch or less. Comments?
The other length I'm curious about is what Telewave refers to as the phasing cables. These are the cables between the cavities and the antenna TEE. Their documentation states these cables should be 1/2 wavelength at the reject frequency. The lengths of the RG-214 cables on this duplexer are both the same and only 13.5 inches long tip to tip.These seem way short since 1/2 wave cables at these frequencies is 26 inches and change. Comments?
73 and aloha, Eric KH6CQ
? ?
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Re: TPRD-1554 Troubleshooting
If it's the cavity on the antenna side, more than likely it took a lightening hit.
Replace the capacitor and you should be fine. Just make sure you get the highest voltage one you can find.
I would pull the other loops apart and clean up the green stuff.
Joe - WA7JAW
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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 Sat, Jan 16, 2021 at 06:59 PM, Eric Fort wrote:
What does one get for going the commercial box route vs the 2 transceiver route with a controller Tying them together?
Eric
Af6ep
Typically one gets a receiver with a tuned preselector front end, a decent IF response curve, and god squelch circuit action, as well as a transmitter that has much lower phase noise with a factory repeater over two mobiles. These features greatly increases ones chances for a succesful project instead of one full of challenges. This applies to most of the ham grade repeaters out there on the market right now ie..(Yaesu Fusion, Icom D-Star, Bridgecom), as most all of them are just 2 mobiles in a box with a controller. One other thing is that if you are planning on installing the repeater on a commercial site, a lot of site managers require part 90 certification and will want the FCC ID numbers off of the equipment before you get it in the building. A factory repeater will be a big advantage and your best friend in these situations. The old saying applies here...Just because you can do it, doesn't mean you should do it. Joe - WA7JAW
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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 mobile radios are seriously deficient in many aspects when put into repeater service. Purposeful repeater stations are generally designed to higher standards.
Duty cycle of mobile transmitter 25% vs 100% for a repeater grade station
Frequency stability, example mobile 5ppm and repeater 2ppm or better.
Transmitter noise , repeater transmitters are designed to minimize TX noise and out of band spurious signals
Repeater transmitters generally have built in circulators and following harmonic filters to reduce site Inter-Modulation Distortion (IMD) and to properly match duplexer impedance.
Receiver selectivity and spurious response. Proper repeater receivers are designed to reject signals off channel adjacent to them as well as out of band spurious. (I was burned on this once with a commercial product that used repackaged mobiles). They will have narrow preselector filters in the order of 1 to 4 MHz versus a mobile having a "wide front end".
?
They will also use high intercept point, low Inter Modulation Distortion (IMD) devices in the RF stage, whereas a mobile is designed for low power consumption and high sensitivity.
Shielding. Mobile radios have insufficient RF shielding . Proper repeaters use feed through filters and seperate the RX and TX sections into RF isolated cans so that they do not interact, nor do they cause or receive interference from other stations on site.
Interface options. Proper repeaters can be easily interfaced with and control and be controlled with external devices.
Duplexers are a related topic. So called flat pack duplexers only serve to reject the transmitter carrier and noise from the receiver. They provide no protection from other stations on site. A band pass-reject filter is the minimum acceptable for a shared site.
You really get what you pay for if you lash together two mobiles or portables and call it a repeater. It may work or not.
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On Sat, Jan 16, 2021 at 09:59 PM, Eric Fort wrote:
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.
? -- The Real RFI-EMI-GUY
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Karl Shoemaker
Matt Wagner
RFI-EMI-GUY