I do not know about the RF Amp they use if it could be modified
to work on our 220 Band.

It's quite possible and relatively straight-forward to move a lot of
amplifiers up and down to a new desired band segment. The physical
construction of the amplifier can lend itself to being a modification
candidate. If the form of the amplifier construction, lends itself
to modification(s), then the devices can be evaluated for operation
at the new location (frequency). You might "get away with" operating
the existing transistors a the new location, or you can replace the devices
with better, more optimal (in this example) for 224 MHz operation...
transistors/fets.

I once moved a VHF Micor style PA up to 224 MHz, it was a major pain
in the a$$ and the results were barely 35% of the 152 MHz operation,
mostly because the gain of the transistors, falls off pretty fast. Did the
same thing moving an 800 MHz Micor PA up to 906 MHz, fairly similar
results. But back in the mid 1980's 35 watts on 906 MHz was worth
operating and putting the effort in to doing, because of limited available
alternatives.

We can share that you can buy a VHF TPL, MFJ, RF Concept, 100
Watt VHF/UHF mobile amplifier and rebuild/rework it down or up on to
the 224 MHz band. Again, certain brands and models better lend
themselves to this type of project.

Addressing a few reader concerns... yes, it's a mobile amplifier
with RF sensed "TR" (transmit-receive) switching. The input relay
and TR system can be bypassed easy enough. Others of you have
concerns about the heat buildup. Put the darn thing in a wind tunnel
box and have two fans moving constant air past the heat sink. You
might notice this method is used in some current amplifier products
to reduce the form factor (size) and increase the duty cycle (tuna-fish).

Other more creative types can relocate an amplifier board/circuit on to
a new/larger/faster/bigger/narley/beefier heat sink. Lazier people like
Liberal Democrats can just roughly bolt more heat sink material on to
the existing amplifier, and additionally blow air across the surface(s).

Certain TPL amplifiers are often made up of modules and those modules
lend themselves to relatively easy modification & access. The power
combiner portions of the circuit can be resized for the 224 MHz range,
and there should be no shocking surprises. Part value changes where
required follow fairly well known rules and requirements. Where 60 to
120 Watt level - mobile TPL Amplifiers used/dead/still working can often
be had for a bargain... to the patient and resourceful ham willing to take
on a project.

And many RB Group Members have completed this type of modification
method, numerous times.
They've just not mentioned it before because now the price of a used,
dead, mouse-pee'd on, dusty, muddy, Ebay, flea market, girlfriends
hope-chest found 80 to 100 watt TPL (or similar) amplifier will rise up
past reasonable... but you can always keep your eyes open if you
want to be resourceful and save some money.

cheers,

Milcom Crescend

This question is for all the 220 MHz repeater owners on the list.
We have a 25W repeater and would like to add an amplifier.

Do we actually have to own a 224 MHz repeater to answer these
questions?

I’m really looking for options other than Henry and TE Systems
but not seeing very many.

There is not yet a practical reply in the queue because you
should provide an answer to the following question(s).

Do you want to buy a complete and ready to operate ("plug
and play") amplifier, or would you be willing to modify or repair
an existing product? Even more involved, would you consider
actually building an amplifier? .... from scratch? from parts?
from a parts donor amplifier? ... from your neighbors discarded
microwave oven?

As with that famous pine tree... many parts are edible. We might
like a better idea of what you're willing to chew on.

cheers,
Grape Nuts

开云体育

开云体育

At 9/15/2018 05:31 PM, you wrote:

Matt W6KGB makes darned GOOD preamps - the performance is equal or
better than the no-longer-available Anglelinear in every way (and
a helluva lot better than ARR, in fact the last time I was in
Matt's shop he was repairing a few dead ARRs for a customer in
the midwest).

I 2nd the above, though with all the duplicated messages on Yahoogroups lately this may turn into a 3rd, 4th, 5th,...

Bob NO6B

As the subject line says, I'm looking to contact
Mike Perryman K5JMP in the Virginia area.

The info I had is no longer any good, and the email
address on QRZ doesn't bounce, but no response.

And trying k5jmp@... (the contact email address
on his QRZ web page) results in a bounce...

Thanks in advance

Mike WA6ILQ

Good morning,

This question is for all the 220 MHz repeater owners on the list.

We have a 25W repeater and would like to add an amplifier as it hears much better than its transmit coverage. Our exciter output is variable from 1 to 25 Watts. Our antenna is a DB224-JJ.

What type of amplifier are you using? I’m really looking for options other than Henry and TE Systems but not seeing very many.

James Adkins, KB0NHX
Repeater Trustee - Nixa Amateur Radio Club, Inc (K0NXA)
www.nixahams.net

So, if you have the choice... or the luxury of comparing and using
a ARR432VDG or ARR460VDG.... one might consider the ARR432VDG
even though it might not be something viewed or selected at first
glance. The ARR432VDG examples I recently evaluated are better
performing preamplifiers when compared to their ARR460VDG cousins.

I've tuned many an ARR preamp. They did make very minor changes during the
life of the VDG series, but if you compare a P432VDG and P460VDG of the same
vintage, they should have the same components, just with different tuning of
the input cap.

As you saw, you can improve the input match somewhat by tuning the input
away from the point of lowest noise figure. At the point of best match, the
NF will be above 1 dB. For repeater service when the preamp is following
filtering, this is often a better trade-off - I'll take the improved match
over the fraction of a dB of noise figure any day.

The input network on the ARR's is about as simple as you can get. The
series trimmer cap and shunt coil on the gate form an LC high-pass network
that coarsely transforms 50 ohms to the high-Z of the gate. You can improve
the match by adding adjustable shunt C in parallel with the inductor.
High-Q caps are necessary to keep the NF low.

As I'm sure you know, you can't test GaAsFET preamps with a VNA at high
power. This is a problem if you have a VNA that has a fixed output level,
or only adjustable over a small range like -10 to +10 dBm. As you start to
approach the compression point, obviously the gain will fall but also the
input match will change. I usually sweep them at -40 dBm input power.

--- Jeff WN3A

ARR Preamplifier Comparisons

I had an brief short amount of spare time to compare (and optimize)
some used ARR receive preamplifiers, models ARR432VDG and
ARR460VDG. Being specified for sale within a 50 MHz design
spacing or distance, one might think they would be a same or a
very similar circuit.

The following described recent observations are essentially the
same as recorded (by me) through the years from a respectable
number of similar preamplifier evaluations and technical conversations.

The ARR432VDG and ARR460VDG appear similar in construction,
with modest variations. However, slight differences in their circuits
do notably affect performance in different S parameter results.

The ARR432VDG (VNA 2-port_2-path) S11 return loss was over
11 dB, which is quite a bit better than many reported values for ARR
preamplifiers of this type. The ARR460VDG value here was just
over 6 dB, which is more in line with measured values reported by
other persons. It's not obvious by casual (visual) observation, why
the ARR432VDG achieves this much better return loss number, but
the devil is in the details... where those details are the value(s) and
type of parts used ins the input matching section/portion of the
circuit.

Gain values for both preamplifier models were above 14dB, but again
the ARR432VDG provided above 16dB to 18dB (gain). The best
gain was not coincident with best return loss as described below.

Moving along...

Of special note, maximum gain does not occur with best return
loss. best return loss does not occur with the lowest noise figure,
and lowest noise figure does not occur with the maximum gain.

In the real world, the above values seem to be relatively close, but
never the same. If you're all about other opinions, I will write that I had
a few different conversations about this subject with Chip Angle,
and he confirmed these observations as valid with his products. Of
course you also have to add stability to balance the preamplifier
design along with all the above mentioned.

The trade of max gain versus best return loss and stability is an
interesting (can be life-long) animal to study. Purest types most often
insist the best match is always the most efficient (return loss). Other
types try to justify their opinions based on more empirical observations
and/or measurements. In the long term scheme of the things, everything
is of course, a mix of trade-offs.

I did measure both the ARR432VDG and ARR460VDG performance
when optimized by the single internal adjustment capacitor, from
about 430 to 470 MHz. It was interesting to note the ARR432VDG
clearly outperformed the ARR460VDG even up in to the commercial
radio band segment approaching 470 MHz. I have seen this trend
in other brands/models preamplifiers, why this occurs, is a whole
additional and probably quite long thread post for another time.

So, if you have the choice... or the luxury of comparing and using
a ARR432VDG or ARR460VDG.... one might consider the ARR432VDG
even though it might not be something viewed or selected at first
glance. The ARR432VDG examples I recently evaluated are better
performing preamplifiers when compared to their ARR460VDG cousins.

Your mileage will of course, vary.


that is all

cheers

Kelvin Scale

Matt W6KGB makes darned GOOD preamps - the performance is equal or
better than the no-longer-available Anglelinear in every way (and
a helluva lot better than ARR, in fact the last time I was in
Matt's shop he was repairing a few dead ARRs for a customer in
the midwest).

Mike WA6ILQ

Ed,

For conventional ID is generally done via CWID during between transmissions, generally every 15 minutes for commercial and public safety. If a user keys up it overrides the ID and re-tries during the next period of inactivity.

Trunking is a different story. Due to the disruption that a CWID would cause, particularly on a control channel, there is an alternative ID scheme where the ID is contained in the data stream. The FCC (or anyone who can do a little bit of research on the internet) can decode this easily.

Voice IDers are unnecessary and waste resources. If you absolutely must have one at least use something that doesn't sound like a computer voice from 1985.

The purpose of an ID is for legal compliance ONLY. Any other use is just utilizing it as a convenience and should not be catered to. ID your station using the method that has the least impact on users and the least utilization of the hardware (Key-up time) and call it good. If you must have a voice ID please follow my recommendation to use the wireline (4-Wire Analog or V.24 from a DIU) and set it to the lowest priority so your users will not be impacted and can key over it. The CWID should still be enabled to ensure compliance even whe the voice ID is overridden. This should be set so that it doesn't encode PL/DPL so that the impact to users is minimized.

Dan Woodie, CETsr
KC8ZUM

On 9/14/18 12:11 PM, 'Jeff DePolo' jd0@... [Repeater-Builder] wrote:

I have a question for the Quantar users. When we narrow
banded (Part 90), I had a P25/Astro CAI quantar that would
not receive three or four out of 50 XTL Mobiles (all mobiles
have the same codeplug). When I looked at the programming, I
had set the Receive Channel BW to Narrow 12.5 KHz. Opening
up the bandwidth to Narrow 12.5 -15.0 KHz, solved the
problem.

Sounds to me like the few "bad" mobiles are either off frequency or the
two-point modulation isn't aligned correctly. As far as the latter issue,
if the reference oscillator mod is wrong, it could be over-shooting the low
frequencies, which has a similar effect to the carrier being off frequency,
albeit swinging both high and low.

^ TSRH

The quantar has a different sort of receiver, it's second IF is direct to DSP,
and the demod is done in the DSP chip on the SCM. They are very sensitive to
lack of deviation in p25.

The 900 MHz requires an external reference, so I'm going to assume it's not
the repeater being off frequency.

The other thing is the 12.5-15 KHz setting is normally used at 900 MHz, but
only if you're running "noise canceler" (aka hearclear). For P25 only, 12.5
only is better as you get about 20 dB more adjacent channel performance. If
you don't need this, there's no issue with running 12.5-15 KHz on receive, the
transmit is still 2.5 KHz.

It's likely these XTL's are suffering at the edges of your receiver area too,
you should really identify and check them out.

--
Bryan Fields

727-409-1194 - Voice

It sure would help if you would quote the post you are talking about
rather than make many of us guess.

Mick - W7CAT

I have a question for the Quantar users. When we narrow
banded (Part 90), I had a P25/Astro CAI quantar that would
not receive three or four out of 50 XTL Mobiles (all mobiles
have the same codeplug). When I looked at the programming, I
had set the Receive Channel BW to Narrow 12.5 KHz. Opening
up the bandwidth to Narrow 12.5 -15.0 KHz, solved the
problem.

Sounds to me like the few "bad" mobiles are either off frequency or the
two-point modulation isn't aligned correctly. As far as the latter issue,
if the reference oscillator mod is wrong, it could be over-shooting the low
frequencies, which has a similar effect to the carrier being off frequency,
albeit swinging both high and low.

Personally, I wouldn't band-aid the problem by widening the IF on the
repeater receiver. If the mobiles are wrong, their performance is being
degraded. Widening the repeater receive IF may allow them to appear to work
under strong-signal conditions, but most likely performance is going to be
degraded when those radios are transmitting into the repeater from
weak-signal areas.

--- Jeff WN3A