[arm-allstar] simpleusb / channel driver merge status?

Mon Oct 2 09:44:06 EST 2017

Richard, you stated you have an isolator on the transmitter. Do you have a second harmonic filter after the isolator? Also have you done a full intermod study on the site including the if frequencies? That may answer some questions. 

Stan

Sent from my iPhone

> On Oct 2, 2017, at 9:38 AM, Doug Crompton via arm-allstar <arm-allstar at hamvoip.org> wrote:
> 
> While they are expensive repeaters in high RF areas should use an isolator
> (circulator) on the TX line to the duplexor. This not only reduces external
> RF from entering the the transmitter and producing possible intermod
> products but also protects the transmitter from a high SWR should something
> happen to the antenna. Many commercial towers require their use. Stick a
> watt meter on the antenna and you often see watts of out of band power
> coming down from the antenna in a high RF area.
> 
> 
> *73 Doug*
> 
> *WA3DSP*
> 
> *http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*
> 
> 
> 
> On Mon, Oct 2, 2017 at 10:25 AM, "Richard Bateman via arm-allstar" <
> arm-allstar at hamvoip.org> wrote:
> 
>> Hi David,
>> 
>> Yeah, I'm actually getting both of those issues =] I don't think the
>> echo issue is actually related to desense in this case, though, I
>> think we have a mixing product somewhere.  I've got an extra bandpass
>> cavities on both sides and I've done some tests and the sensitivity of
>> the receiver does not seem to be meaningfully impacted when the
>> repeater is transmitting.
>> 
>> The random keying issue could well be something like you suggest;
>> oddly, only that repeater of the 4 on the same tower is affected and
>> while I am using some LMR400 on the tower still, it's all very new
>> (temporary while we make sure our antenna setup is where it will be)
>> and this antenna is actually the one that *is* using heliax.  I've
>> also got an isolator on this one, but there isn't on most of the other
>> ones. If the issue happened all the time it'd be a lot easier to track
>> down, of course =]
>> 
>> That does remind me, though, that I don't think I've put the antenna
>> analyzer on the full antenna system -- I know the antenna itself was
>> very very good (something like 1.15:1) when I put it up, but I haven't
>> tested it through the feedline or through the duplexer and I should do
>> that.
>> 
>> Lots of things to try, little time to go up on the mountain this week
>> =] Gotta get part of the house ready for my sister whose family needs
>> a place to stay for a couple of months as they relocate. Life is
>> always interfering with my repeater work... *sigh* ;-)
>> 
>> I appreciate your thoughts and feedback; I'll keep testing and trying
>> things.
>> 
>> Richard
>> 
>>> On Mon, Oct 2, 2017 at 5:32 AM, David McGough <kb4fxc at inttek.net> wrote:
>>> 
>>> Hi Richard,
>>> 
>>> If your situation is that the repeater is just randomly generating an
>>> active COS signal when its transmitter is un-keyed, this is most likely
>> an
>>> RF intermod or other interference problem. If you're at a site with
>>> broadcast transmitters, something intermittently arcing (diode noise) is
>> a
>>> likely suspect. Look for (and remove/replace!) any loose, rusted/corroded
>>> hardware near your RX antenna.
>>> 
>>> If the repeater is getting back into itself so that you hear an audio
>>> echo, this is most likely severe desense from the repeater's own
>>> transmitter. Is the problem reduced/eliminated if you turn the
>> transmitter
>>> power down (temporarily)??
>>> 
>>> Some antennas and types of feedline are more susceptible to PIM (passive
>>> intermod) generation than others. For example, in general, it's best to
>>> stay away from LMR style coax---any style that has a tinned braid over
>>> aluminum foil (dissimilar metals). While LMR coax may work fine when
>>> initially installed, after a few years, once a little corrosion has
>>> started between the braid and foil, it starts causing noise problems.
>> Some
>>> style of heliax is preferred.
>>> 
>>> ....Your antenna system needs to be virtually "perfect," of course, if
>>> you're using a duplexer, or your TX will probably interfere with the RX.
>>> 
>>> Without knowing more about your RF setup, it's hard to do more in depth
>>> diagnostics??
>>> 
>>> 
>>> 73, David KB4FXC
>>> 
>>> 
>>>> On Sun, 1 Oct 2017, Richard Bateman wrote:
>>>> 
>>>> Yeah, I'm using the URIx.  I'm having a couple of issues, but the one
>>>> I'm trying to deal with right now is basically that there is some kind
>>>> of noise that keeps keying up the repeater and we can't figure out
>>>> where it is coming from. It might well just be that it's RF noise and
>>>> we need to track it down, since I hear it when the repeater's squelch
>>>> opens and there is no signal to listen to, but on the spectrum
>>>> analyzer it's not strong enough to come out of the noise.
>>>> 
>>>> Sometimes it'll sit there kerchunking over and over again, multiple
>>>> times per second, despite the PL tone on the receive, and other times
>>>> it's quiet as you could ask for. Putting an extra ground wire as you
>>>> suggest sounds like it'd be worth a try to me =]
>>>> 
>>>> One reason I've been considering trying dsp-based is to find out for
>>>> sure if the issue is in the RF signal or if it's in the CTCSS/COR
>>>> signalling when they shouldn't (for whatever reason, whether the
>>>> radio, which is a TKR-750 version 1, or some electrical issue like a
>>>> ground loop).
>>>> 
>>>> Richard
>>>> 
>>>> On Sun, Oct 1, 2017 at 7:44 PM, David McGough <kb4fxc at inttek.net>
>> wrote:
>>>>> 
>>>>> Hi Richard,
>>>>> 
>>>>> Are you using a URI or URIx audio adapter?  If so, I've had superior
>>>>> results by adding an extra, heavy-gauge ground lead to the URI. Then,
>> I
>>>>> directly connect this lead to the repeater chassis--a screw on a
>> Kenwood
>>>>> TKR repeaters...This has been my #1 ground-loop solution.
>>>>> 
>>>>> Here are a few sample photos:
>>>>> 
>>>>> https://hamvoip.org/kenwood-TKR/P1030817.JPG
>>>>> https://hamvoip.org/kenwood-TKR/P1030820.JPG
>>>>> 
>>>>> Test TKR-750-2 repeater on bench:
>>>>> https://hamvoip.org/kenwood-TKR/P1030831.JPG
>>>>> 
>>>>> ALSO -- on the TKR750/850 repeaters, make sure to notice that the
>> 25-pin
>>>>> accessory plug has separate analog and digital grounds!
>>>>> 
>>>>> If you've got RF or other noise issues with simpleusb telemetry, I
>> doubt
>>>>> switching to usbradio DSP-based signaling will fix anything. Try
>> running
>>>>> the TX into a dummy load and test, if possible.
>>>>> 
>>>>> 73, David KB4FXC
>>>>> 
>>>>> 
>>>>>> On Sun, 1 Oct 2017, "Richard Bateman via arm-allstar" wrote:
>>>>>> 
>>>>>> Hi,
>>>>>> 
>>>>>> I've been having some issues that I'm starting to suspect might be
>>>>>> related to RF getting into my interface cables triggering my COR and
>>>>>> CTCSS lines (not in any way convinced, but it's on my list of
>>>>>> suspects) and have been toying with the idea of using usbradio
>> instead
>>>>>> of simpleusb for awhile; last time I did that the audio was kinda
>>>>>> crappy, so I switched to simpleusb.
>>>>>> 
>>>>>> While looking around I noticed that there is a "TODO" on the hamvoip
>>>>>> page about merging the channel drivers, which I assume might be
>>>>>> something along the lines of using DSP for COR and CTCSS detect but
>>>>>> using the other audio for actual TX?
>>>>>> 
>>>>>> Anyway, I'm just wondering what the status of that is and if there is
>>>>>> any way I can help with the efforts; it would help me out a lot on
>>>>>> several different projects.
>>>>>> 
>>>>>> Richard
>>>>>> _______________________________________________
>>>>>> 
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>>>>>> 
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>>>>>> 
>>>>> 
>>>> 
>>> 
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>> 
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>> 
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