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Re: VHF MTR2000 Poor Receive Performance
So last night, I measured the MTR at 0.4uV at the receiver port and 0.5uV at the duplexer antenna port.
I injected a signal into the receiver port of the MTR that had just barely had no noise and when I injected it through the duplexer into the repeater, there was noise present. It wasn't heavy noise but it still had noise on the signal. |
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Re: Connecting Yaesu DR2X Repeater to Raspberry Pi/Allstar?
Here is a link to a program called PiTone which can be used to create a CTCSS tone.? PiTone runs on a Raspberry Pi (can be the same one that is running Allstar).? It uses a D/A converter connected to the I2C bus to create a stepped sinewave which is easy to filter to a "pure" sinwave.
We have used it on our local repeaters (DR-1X and Micor) for more than 4 years. Steve - N8AR |
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Re: VHF MTR2000 Poor Receive Performance
¿ªÔÆÌåÓýJared,
We need to quantify why (and when) the repeater is "deaf". Next time you're at the site, do the following: 1 - Disconnect the repeater from the duplexer.? 2 - Connect the repeater antenna to the receiver - directly.? 3 - Terminate the transmitter into a suitable dummy load. 4 - Get a friend to help or use the service monitor to produce a weak signal into the repeater.? This must be a stable emission that's repeatable.? It can't be full quieting - some noise needs to be preset to detect a change in quieting. 5 - Reconnect the antenna to the duplexer, and receiver to the duplexer, but do NOT connect the transmitter - - leave it on the load. 6 - Compare the signal quality (quieting) between the antenna being connected directly to the receiver and additionally through the duplexer.? At 1.67 dB IL - they should be virtually identical. ** If there is little/no difference between the signal level with the antenna connected directly to the receiver and through the receive path of the duplexer, the 'disappointment' is not the duplexers' fault.? You could swap in a different receiver, even a HT temporarily to see how well it hears in comparison.? Just remove whatever you substitute and reconnect the repeater's receiver before you continue. 7 - Remove the transmitter from the load and connect the transmitter to the duplexer. 8 - Wire a toggle switch into the PTT lead to instantly disable the repeaters transmitter. 9 - Compare the weak signal with the transmitter "ON" and "OFF".? They should be virtually identical. A - If there's a notable difference in quieting with the antenna connected directly to the receiver and then through the receive path of the duplexer - the RX path insertion loss isn't really 1.67dB. B - If there's a difference in quieting between when the repeater transmitter is on and off - you have classic desense. Let us know the results. Kevin On 11/1/2022 6:55 PM, Jared Smudde wrote: So the transmit side cavities all have 29db-32db of return loss at pass frequency, 30db of notch rejection and 0.4db of IL at the pass frequencies. |
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Re: VHF MTR2000 Poor Receive Performance
I think we need to redefine 'deaf'. What are the current 12dB SINAD 1) at the receiver port, and 2) at the antenna port of the duplexer? (Those values were previously reported as 0.40 and 0.53 uV respectively.)
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Originally the problem was reported as " basically deaf to 5 watt portables barely a mile from my house, mobiles work a bit further" and about 1 dB of desense was reported. We need to make sure we're comparing apples to apples. At this point, portable or mobile coverage and anything to do with the antenna system (except the duplexer) needs to be OUT of the equation. Measurements all need to be made using the same test cables and the same signal generator/service monitor. Anything else introduces errors/uncertainties. The receiver itself (with no TX engaged) needs to be baselined to see if it meets specs (0.35 uV for 12 dB SINAD I believe), and if it does not, that needs to be addressed. Adding in the duplexer, sensitivity should decrease only by the amount of loss previously recorded in the Pass. If the Pass is measured as 'X' and the receiver sensitivity decreases by more-than-'X', than something is amiss at the Circle K and investigation needs to determine the cause. Sometimes it's helpful to take a day off, go poke .45 caliber holes in paper, then come back to it with a fresh mind, starting over at square one. My 2-cents worth. Mike WM4B -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of MILLIN SEE Sent: Tuesday, November 1, 2022 8:09 PM To: [email protected] Subject: Re: [repeater-builder] VHF MTR2000 Poor Receive Performance Sounds like your forcing that duplexer outside it's parameter. Millin ----- Original Message ----- From: Jared Smudde <computerwhiz02@...> To: [email protected] Sent: Tue, 01 Nov 2022 16:55:15 -0600 (MDT) Subject: Re: [repeater-builder] VHF MTR2000 Poor Receive Performance So the transmit side cavities all have 29db-32db of return loss at pass frequency, 30db of notch rejection and 0.4db of IL at the pass frequencies. I went to the receive cavity causing trouble and slid the tuning rod all the way up and cleaned the rod with some fine sandpaper and wiped it down with denatured alcohol. I then took the rod and ran it up and down the cavity several times all while rotating the rod at the same time. I was able to get the return loss to 30DB on the cavity. Probably had to clean some varnish off of the rod and tuning fingers. I reattached the harness and each side had about 1.67db of insertion loss and I was able to get the notch over 105db on each side. I hooked up the repeater and was met with disappointment, repeater is still deaf with no improvement. |
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Re: VHF MTR2000 Poor Receive Performance
So the transmit side cavities all have 29db-32db of return loss at pass frequency, 30db of notch rejection and 0.4db of IL at the pass frequencies.
I went to the receive cavity causing trouble and slid the tuning rod all the way up and cleaned the rod with some fine sandpaper and wiped it down with denatured alcohol. I then took the rod and ran it up and down the cavity several times all while rotating the rod at the same time. I was able to get the return loss to 30DB on the cavity. Probably had to clean some varnish off of the rod and tuning fingers. I reattached the harness and each side had about 1.67db of insertion loss and I was able to get the notch over 105db on each side. I hooked up the repeater and was met with disappointment, repeater is still deaf with no improvement. |
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Re: Windows 7 config
I am not using a repeater. Just using vara fm and winlink. Will be using a cdm1250. Just looking for information on the software side. Sorry for stirring the pot
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Re: Somewhat OT... imaging a hard drive...
I know it has been proposed?but I use ? it works on any pc, 32 bit or 64. And if you plug a MAC SATA disk into an external drive bay it will even make a nice image of it or even duplicate it to a new drive.Works on IDE and on SSD's even works on USB attached drive.? Simple GUI and the main thing, it is free! Le?lun. 31 oct. 2022 ¨¤?14:49, wj9jrg <wj9jrg@...> a ¨¦crit?:
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Re: Windows 7 config
Ok...I obviously missed the data part lol... Chris WB5ITT? On Tue, Nov 1, 2022, 12:59 PM Scott Currie <scott.d.currie@...> wrote: Correct, we're not talking about repeaters here. We are taking discriminator audio to the sound card interface for decoding, and sending modulated data from the sound card to the modulator. Obviously if you set the transmit gain too high you will cause interference on adjacent channels. And it will also destroy the data being sent, so a really bad idea. |
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Re: Windows 7 config
Correct, we're not talking about repeaters here. We are taking discriminator audio to the sound card interface for decoding, and sending modulated data from the sound card to the modulator. Obviously if you set the transmit gain too high you will cause interference on adjacent channels. And it will also destroy the data being sent, so a really bad idea.
This discussion would be better handled on the Winlink and Vara forums: /g/VARA-MODEM/topics -Scott, NS7C |
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Re: Windows 7 config
I strongly disagree Scott... That's a recipe for disaster. Feeding wide band unsquelched noise to a modulator will cause the transmitter to over deviate. Remember the squelch noise out of a discriminator is half the bandwidth of the IF filter which means you have audio at 7.5 khz + coming out of the receiver.. Anytime I run flat audio, I always put a clipper/limiter circuit in line to prevent over deviation, and also to limit the audio bandwidth to 3 kilohertz maximum. Under FCC part 97 rules we are required to make sure that we use good engineering practices. Running raw discriminator audio straight into a transmitter modulator without any processing violates that rule. I've done that in microwave systems but that's a special case and you have the bandwidth to do it. In the crowded VHF/UHF bands, it's totally ludicrous to do so Chris WB5ITT?
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Jared Smudde
Steve-N8AR
Kevin Custer
Karl Shoemaker
Mike Besemer - WM4B
SCOTT READ - KM6RFB
Pierre Martel
Chris Boone WB5ITT
Scott Currie