Re: R266A -Spectrum analyzer ghosts (internal signals)
Thanks for the reply. These signals are internal. All the boards are mounted in a giant metal card cage and are very well shielded. Not sure what else to check at this point.?
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Re: R266A -Spectrum analyzer ghosts (internal signals)
Terminate the RF input with a dummy load when testing this. As to if it is normal, there are a lot of internal signal sources that could intrude. I would suggest checking all the shields, fasteners and connectors for tightness. If any shields or connectors are corroded be sure to clean up appropriately and use de-oxit.
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The Real RFI-EMI-GUY
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
Now I¡¯m even more baffled than before lol. The original receiver is passing audio to the rx pin just fine in both jumper positions.
WZ5TX
David ¡°Tyler¡± Bufkin
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Just glancing at the schematic:?? You can't be missing discriminator audio if you have speaker audio.?? Unless your J551A jumper is bad or something near there (circled).
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
Just glancing at the schematic:?? You can't be missing discriminator audio if you have speaker audio.?? Unless your J551A jumper is bad or something near there (circled).
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
Yes, I am going to get the scope out trace it from the rear and see where it stops outputting a signal for starters. Since this is the second one to do this, I¡¯m wondering if voltage is either spiking or coming through it from the SC50 or maybe
even the controller
WZ5TX
David ¡°Tyler¡± Bufkin
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You don't have a bad Xtal then.?? You will have to download the schematic and troubleshoot.
Andy
Yes I am getting the 44.645 signal.
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
You don't have a bad Xtal then.?? You will have to download the schematic and troubleshoot.
Andy
Yes I am getting the 44.645 signal.
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Re: Stationmaster type antenna available, 152 MHz., Nashville, TN
- Shall I call them back and they¡¯ll them they are wrong??
I wouldn¡¯t call them and tell them they are wrong because they¡¯ll probably hang up on you.? I would ask them to explain the physics behind what they are telling you as it doesn¡¯t make sense.
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Re: Help with out of range programming a Motorola GP300
Thanks for the guidance.? Looks like these have no ability to become "new ham intro radios" for the local repeaters.
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Alex, the shift trick definitely does not work when trying to go up in frequency.? I havent tried going down, since there's no legal spot to move it down band...?
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When using the shift trick, The RSS chokes on input and reverts to the originally programmed channel with a warning noting the frequency limits of the radio.
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I know it works on some of the other Radius and Maxtrac RSS programs, as I've successfully gotten those radios into the ham bands, and still support a number of old timers with those radios as new repeaters come on line and the radios need updating.
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They are nice little radios, and I had hoped to reprogram and give them away, but it seems they will not be useful.? Maybe I'll try to set them up as low power Allstar nodes for a connection around the QTH...
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ron
KA3JIJ
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Re: Stationmaster type antenna available, 152 MHz., Nashville, TN
Been there, done that and every inch of the antenna is in perfect condition and I shared that with Commander Technologies who now makes this antenna and told me 427MHz is about right for 6 degrees of downtilt at 449Mhz. Shall I call them back and they¡¯ll them they are wrong??
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
Yes I am getting the 44.645 signal.
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
Another way you can tell is if you have a communications receiver or a service monitor.?? Tune to 44.645 Mhz and you will hear a carrier emitting from the radios (shields off).?? It may be a little weak so you might have to couple your receiver near that IF Xtal.
Andy
So .... Do you get that good audio from the speaker from weak signals??? Can .5 uV signals with audio result in audio from the speaker??? If so, your XTAL is good.
Andy
I may need to be a little more clear¡.:I still get RX audio from the speaker just none from the pin on the rear. All I get from the pin on the rear is dead audio with pl(otherwise the pl encoder would not give a valid cos)
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
So .... Do you get that good audio from the speaker from weak signals??? Can .5 uV signals with audio result in audio from the speaker??? If so, your XTAL is good.
Andy
I may need to be a little more clear¡.:I still get RX audio from the speaker just none from the pin on the rear. All I get from the pin on the rear is dead audio with pl(otherwise the pl encoder would not give a valid cos)
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
I may need to be a little more clear¡.:I still get RX audio from the speaker just none from the pin on the rear. All I get from the pin on the rear is dead audio with pl(otherwise the pl encoder would not give a valid cos)
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Re: Motorola GM300/Maxtrac rear rx pin not passing audio
I should have been more specific. I don¡¯t get the COS signal from the radio. I get the COS from the masters SC-50 micor squelch pl board¡ I will get some crystals ordered! Thank you
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Taking these suggestion in and it should keep me busy for a few months.... external power supply (have), fix PS/caps, power switch clean and test... THANKS to all!
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Re: Stationmaster type antenna available, 152 MHz., Nashville, TN
Had a grain silo place where we had some equipment complain about "our" antennas laying in the corner of the roof. Well, not our antennas, they were left over paging customers. But, we decided to clean the roof up. How do you get down a 20 foot antenna in a 10 foot elevator? I cut them apart with a Milwaukee battery operated saws-all. Kinda fun.
If you ever have a very high frequency (this one was listed at 158 MHz,) SWR was really laughable in the 2 meter band, cut it open . The construction is fun to look at. It's like 1'2" to 3/4" rigid line, with the inner and outer conductors flipped from time to time.
Matter of fact, here's a challenge. Anyone have a non-useful Station Master or equivalent? Bring it to Dayton, and we will cut it apart and it can be a Scom "Show-n-Tell" Telling you, kinda cool to look at.
Tom K8TB
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Re: Stationmaster type antenna available, 152 MHz., Nashville, TN
At 4/28/2025 11:09 AM, you wrote:
The reason I contacted Commander
was because I was concerned with the lowest VSWR at 427MHz for a 449MHz
stamped antenna which I picked up second hand. They were able to look up
info from my antenna S/N and they said 427MHz was about right for the
6deg or so downtilt that was ordered for this antenna and the original
owner said it was purchased for a 6,000ft site with 6deg of downtilt.
Commander said older antennas were basically tuned lower in frequency for
downtilt with more downtilt pushing the resonant frequency
lower
Time to pull the guts out of this antenna & see the physics-defying
construction.? Perhaps they run feedline internally up to the top
& feed it from there?
*grabs popcorn*
Bob NO6B
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R266A -Spectrum analyzer ghosts (internal signals)
Hello members, I have an old R2660A (IDEN option) that I replaced all the 33uf electrolytics caps on Interface board ( each one had leaked). Luckily no major damage that didn't clean up. This fixed the alarming of the "excessive power to internal load alarm". I also replaced the memory battery as well. It goes through all calibrations successfully. Everything seams to be working ok except I'm seeing all kinds of internal signals in spectrum analyzer mode (no antenna connected). It does receive signals normally when connected to an antenna.
Does anyone know what might be causing this?
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More bad electrolytics on another board....or?
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I pull the spectrum card and receiver card and check the electrolytics on those and they were fine.
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It what quite a job replacing all those things too i must say...
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Thanks in advance
Randy
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Re: Stationmaster type antenna available, 152 MHz., Nashville, TN
Electrical downtilt is created when the phase of higher elements *leads* the lower elements. An easy way to visualize this is to take a multi-element antenna (a dipole array or whatever is easy to picture in your head) and tilt it to the right. The pattern will have downtilt toward the right because the upper elements are now leading the lower elements referenced to the horizon. Likewise, to the left, the antenna will have uptilt.
As compared to mechanical downtilt in the example above, with electrical downtilt the beamtilt is the same around the 360 degree azimuth.
An end-fed collinear antenna that has phasing sections that are too short will result in upper elements leading in phase. That is, rather than having the nominal 180 degree (half-wave) phase delay between elements for an on-horizon pattern, a shortened phasing element will provide less than 180 degrees of delay, so the further up the antenna you go, the further the radiating elements will be leading in phase. .
Andy was correct in his response - an end-fed collinear antenna like a Stationmaster will have downtilt when operating below its design frequency.
--- Jeff WN3A
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Re: Stationmaster type antenna available, 152 MHz., Nashville, TN
I might add that I carefully tested my SuperStationmaster downtilt by placing it on a 10ft mast and monitored signal level on a spectrum analyzer while tilting it back and forth towards a hilltop repeater. I noted the angle of highest signal level, which ended up about 6deg tilted back away from the repeater site which would indicate downtilt. I tested another antenna with no downtilt and it¡¯s peak signal level was with the antenna mast plumb, or no up or down tilt.?
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RFI-EMI-GUY
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