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220 MHz amplifier
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 |
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Re: ARR Preamplifier Comparisons
So, if you have the choice... or the luxury of comparing and usingI'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 |
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ARR Preamplifier Comparisons
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 |
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Re: Wanted: 220 MHz Preamp
Matt W6KGB makes darned GOOD preamps - the performance is equal or
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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 On 9/15/2018 5:54 AM, k9ic_repeater@... [Repeater-Builder] wrote:
I am seeking a 220 Preamp, maybe Advanced Receiver?P220VDG or similar |
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Re: Voice ID'er for P25 Repeater
Frank Perkins
Hi Ed, Just a thought . . I use a $37?ID-o-Matic IV for my Maxtrac 440 repeater to CW identify, control the fan, etc. They have a small add-on audio board (I think it was $20) to capture hold, and produce a voice identification. The little controller works well and is programmable via a USB cable with laptop running any terminal emulation program. Frank N6CES On Sat, Sep 15, 2018, 12:00 PM Ed McKinney kb8qeu@... [Repeater-Builder] <Repeater-Builder@...> wrote:
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Re: Voice ID'er for P25 Repeater
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 |
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G.E. M7100 radio question
Gary HENDRICKSON
Guys, We've come across some 380 to 400 MHz G.E. M7100 mobile and desktop radios that appear to be programmed for trunked operation. I have 2 questions: 1.? Can they be tuned, or modified, for operation in the 420-450 band, and 2.? Can they be programmed for convention ham type of operation? I'm not al all familiar with this series of radios, so any info would be of help. Thanks, es 73, Gary? W3DTN |
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Re: Quantar Rx Question
On 9/14/18 12:11 PM, 'Jeff DePolo' jd0@... [Repeater-Builder] wrote:
^ TSRHI have a question for the Quantar users. When we narrowSounds to me like the few "bad" mobiles are either off frequency or the 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 |
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Re: Voice ID'er for P25 Repeater
Ed McKinney
I am wondering how can a P25 repeater identifies, even in commercial application at 15 minute intervals? How would the FCC knows it's operational or not? In amateur application, at least a CW IDer. Voice is nicer. HMMmm... ____________________________________________________________________________________________ Seven? Three Ed McKinney - _______________________________________________________________________________ ?????????? an under servitude to the muslims ?????????? in any way or form. ____________________________________________________________________________________________ On Fri, Sep 14, 2018 at 11:55 AM Brett Friermood brett.friermood@... [Repeater-Builder] <Repeater-Builder@...> wrote:
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Re: Voice ID'er for P25 Repeater
It sure would help if you would quote the post you are talking about
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rather than make many of us guess. Mick - W7CAT ----- Original Message -----
From: "Joe Borovetz j.borovetz@... [Repeater-Builder]" To: "Repeater-Builder@..." Sent: Friday, September 14, 2018 11:32:14 AM Subject: [Repeater-Builder] Re: Voice ID'er for P25 Repeater > Items 2 and 3 in the previous post are both wrong. > Radio Reference is the last place that I would even think about looking for P25 hardware information. > You cannot get analog audio out of a P25 repeater at the wireline port when running in P25 mode. > There is enough bad information floating around out there without folks adding to it. > Without a lot of technical expertise and the hardware and software to do so running a voice ID on a P25 repeater in P25 mode is not the easiest thing to do. > Run the repeater in mixed mode operation and feed the ID in as analog audio on the repeater in analog mode. Program your radios to operate in mixed mode. > Even this is difficult unless you know how to program the wildcard settings, I am assuming you are using a Quantar. > > Buy a Northcomm Technologies cable and they will send you the instructions for programming the wildcard settings. > Otherwise be prepared to get into the world of the DIU3000 and V.24 connections to the Quantar. > -- Untitled Document Be sure to check out all the latest at our web site <;! <; 
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Re: Voice ID'er for P25 Repeater
Joe Borovetz
Items 2 and 3 in the previous post are both wrong. Radio Reference is the last place that I would even think about looking for P25 hardware information. You cannot get analog audio out of a P25 repeater at the wireline port when running in P25 mode. There is enough bad information floating around out there without folks adding to it. Without a lot of technical expertise and the hardware and software to do so running a voice ID on a P25 repeater in P25 mode is not the easiest thing to do. Run the repeater in mixed mode operation and feed the ID in as analog audio on the repeater in analog mode. Program your radios to operate in mixed mode. Even this is difficult unless you know how to program the wildcard settings, I am assuming you are using a Quantar. Buy a Northcomm Technologies cable and they will send you the instructions for programming the wildcard settings. Otherwise be prepared to get into the world of the DIU3000 and V.24 connections to the Quantar. |
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Re: Quantar Rx Question
I have a question for the Quantar users. When we narrowSounds 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 |
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Re: Quantar Rx Question
¿ªÔÆÌåÓýThese are all good points Dan Woodie.? These are early quantars, circa 2003 or so all but one, five or six years newer... this entity has five total, and the later model is the one I first had this issue with... The others work in NB Analog only, but due to a PA failure, the newer one was replaced with one of the older ones.? Both exhibited the same scenario with P25 when set up CAI Only and 12.5 KHz bandwidth.? And no, I have not checked the mobiles... not because I didn't want to, but because I wasn't allowed access (they work now... no need to check further).? Yes, the repeaters validate fine.? All aspects of tuning workout beyond specs. The mobiles do talk with the adjoining entity on P25 just fine, just not with their own repeater.? All analog operations seem fine, no distortion, not clipping... so it's a good guess that the mobiles are likely within spec.?DPS has older, Spectra's that also are working just fine with the narrower bandwidth, so I'm not too sure if a firmware was updated and/or available.? I couldn't get anywhere with the remains of the Quantar group at Motorola, so I asked here.? We are looking at a simulcast upgrade to the overall system in the very near future, so these repeaters are all on the short retirement list, and widening the passband is a suitable band aid for the short term.? Thanks for your suggestions... On 9/13/2018 8:49 PM,
kc8zum@... [Repeater-Builder] wrote:
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Re: Voice ID'er for P25 Repeater
Since you didn't quote anyone's message we have no way of knowing what you are talking about or referring to. If by chance you are referring to the original post, anyone that has a P25 radio, receiver, or <$50 in hardware with some ambition and a working knowledge of linux would be able to hear a voice ID broadcast in P25 mode, just as with anything other P25 voice traffic. And unless something changed, audio transmitted in unencrypted P25 voice frames will certainly be heard through a properly programmed P25 radio. |
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Re: Quantar Rx Question
Tom,
Have you tested the actual deviation of the mobiles in question to confirm that they were successfully narrowbanded? The fact that enabling wider receive bandwidth helped makes me suspicious. Widening the RX bandwidth will widen the passband. Have you noticed any distortion or clipping out of the receiver on audio peaks (in analog)? Have you performed the validation check in the Quantar software? What firmware versions are the Quantars? Keep in mind that not every Quantar is narrowband-enabled - some needed firmware updates to enable narrowband. These are now NLA. Dan Woodie, CETsr KC8ZUM |
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Re: Quantar Rx Question
Maybe the Mobiles are off frequency?
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First thing that springs to mind. Not up to speed on P25 related issues, or these particular radios though.. -Dave, KB7SVP On 9/13/2018 8:46 AM, Tom Parker thp@... [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.? Here years later, I swapped out this repeater with another one, and again experienced the same problem.? Can anyone on the group suggest why this would affect only a few of the XTL mobiles, and not all of them? |
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Re: Voice ID'er for P25 Repeater
Ed McKinney
Thank you for the info. It helps a lot! Still miles to go before I sleep! ____________________________________________________________________________________________ Seven? Three Ed McKinney - _______________________________________________________________________________ ?????????? an under servitude to the muslims ?????????? in any way or form. ____________________________________________________________________________________________ On Thu, Sep 13, 2018 at 1:35 PM Tom Swisher wa8pyr.list@... [Repeater-Builder] <Repeater-Builder@...> wrote:
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Re: Voice ID'er for P25 Repeater
¿ªÔÆÌåÓý1. P25 Phase 1 (C4FM) is one transmission per channel. P25 Phase II is two-slot TDMA which gives two voice paths per channel.2. I¡¯d suggest starting with the Wiki which, although it¡¯s geared more to scanner users, does have some decent info on P25. There are some white papers out there elsewhere which go more deeply into the theory behind P25 but I can¡¯t remember where offhand. 3. Yes, you could patch a P25 repeater to an analog repeater, although you need to be careful about where you get the audio. Best bet is probably to use wireline connections so the audio is analog. Tom
--- Tom Swisher wa8pyr.list@... "Democracy is two wolves and a lamb?voting on what to have for lunch. Liberty?is a well-armed lamb contesting the?vote." - Benjamin Franklin
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