[App_rpt-users] Micor Squelch like available on APP?

[Lu Vencl]

Bryan,

Thanks for the info on your configuration. I think I will hold off for now
as I really want to help test out the patches this fall. But if it gets real
bothersome, I might just loosen up the squelch.

The repeater does not get much activity anyway, so an occasional bust should
not be a huge deal, and that's even if I bother to open it up.

As to your noise, this sounds like PIM (Passive intermodulation) that can
occur when you have dirty connections, bad antenna or some other external
active mixing component. If you can get me an audio sample, I would be
interested in hearing this. However possible, I doubt this is static
discharge.

73

Lu

KA4EPS

 

From: app_rpt-users-bounces at ohnosec.org
[mailto:app_rpt-users-bounces at ohnosec.org] On Behalf Of Bryan D. Boyle
Sent: Monday, July 25, 2011 9:07 PM
To: app_rpt-users at ohnosec.org
Subject: Re: [App_rpt-users] Micor Squelch like available on APP?

 

On 7/25/11 7:59 PM, Tim Sawyer wrote: 

Lu Venci, 

 

I found the same issue thought I did not measure it as you have. I reverted
to good-old Micor squelch and P/L reeds because I did not feel that app_rpt
DSP did as well as the Micor  in either case. Sometimes 40 year old
technology is still best.   


I'm doing a hybrid of what you're doing, Tim; Scott Z built my 220 Micor
bringing out both the COR signal and the discriminator audio; I use the
Micor squelch circuit high for COR, and the DSP to decode the tone.  In my
mind, one is a go/no go, the other is something that can be inferred from
simple signal processing.    

carrierfrom=usb
ctcssfrom=dsp

Gives me the best of both worlds (Micor squelch, as you say, thought 40+
years old, is the tops), and the flexibility to change tone without having
to search out reeds (for testing, lid removal, etc.).

I have an issue to throw out...which kind of got me scratching my
head....occasionally (and non-repeatably), when keying up the
repeater...I'll get a building in volume rushing noise (think raster noise
like on an unoccupied TV channel that increases in volume) that peaks and
then goes quiet.  Incoming audio is there all the time...I was thinking it
was desensing, but it is not every time I key up the machine, I've gone thru
the duplexers to tweak them to >90db of notch (after cleaning up the caps
and polishing the copper-to-copper mating surfaces for the coil/cap
assembly...I'll send a photo if anyone is interested...) and am running only
about 55w into the xmt side.  

Coax is 1/2" superflex out to the polyphaser, (I'm not going to admit I have
some other non-recommended from the polyphaser up the pole, ok?  It's in the
plan to replace, I have 140' of LDF4 ready to go...just have to get up on
the roof...), SWR from the radio to the amp is <1.2, from the amp to the
duplexer is <1.2, loss thru the cans is 1.7db, swr out of the cans into the
superflex is 1.2...all audio paths are shielded (but not ground looped, I
know how to build audio channels...), no connector adapters, all
silver/gold/teflon, etc.  

Has me scratching my head.  That it's not repeatable, but happens randomly
has me thinking that it's static discharge?  Pole and tripod are bonded and
grounded, antenna is a stationmaster-type (tram 1494 cut to length, lock
screws in the center radiator are tight and lock-tighted, and it's a dc
ground design, albeit with a fiberglass radome.  

Thinking static build up/discharge?  Something else?  Anyone else run into
this?  We can take this offline, but, seeing as we're all repeater geeks
here...thought I'd throw it out for consideration.  

Thanks all...




-- 
Bryan 
In this world, you must be oh so smart or oh so pleasant.
Well, for years I was smart. I recommend pleasant. 
You may quote me. 
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