Control Station will not receive

[emtprt]

We recently added a control station as a dispatch backup in the event of the loss of phone circuits. The control station is connected to a 4 position Zetron console and has 2 channels programmed in it. We are using a 40watt UHF CDM1250 with a preselector and 9.2dB gain yagi antenna with 40' of 1/2" hardline.

The control station is programmed to work with 2 UHF repeaters in the 453.xxx range. Both repeaters are on the same tower. Repeater 1 is an MTR2000 with a 3.8dB gain omnidirectional antenna on DPL currently wideband. The other repeater is a Quantar analog mode/ narrowband on PL with a 9 dB gain eliptical antenna.

When on channel 1 the control station works great TX/RX. On channel 2 the control station will not receive.

The vendor believes there is co-channel interference. I had them recheck the programming and they stated if was correct.

I attempted to troubleshoot the issue by transmitting into the radio on the receive channel 1 block from the site without success. We also changed antennas at the repeater site and increased transmit power on frequency 2 in an attempt to open the repeater.

Prior to installing the control station had a tech. transmit into another repeater(gr1225 UHF narrowband) on the tower from the roof of the building where the antenna is located with a 4 watt portable. He received the repeater loud and clear.

Would changing to a DPL help or could there be that much interference?

FYI the last round of testing was done on a Sunday afternoon assuming radio traffic would be light.

Thanks

Mark

[Bill_G]

Mark - time for someone to break out a service monitor, check the radio, and do a receiver desense test. Just because it works on one channel doesn't mean it is working well. The radio could be getting clobbered by a co-channel user, but generally that problem comes and goes as the channel is used, and you would hear them when you monitored. It is not a constant failure.

It could be the CDM is listening to a birdie either self induced, from another radio nearby, or even other equipment on site. You should be able to hear that on a portable in monitor. We had a customer with an existing UHF SCADA for their fresh water system. They replaced all the pump controls with new equipment, and suddenly some of the pump sites had intermittent comm failures. It turned out to be the LCD displays on the face of the new panels. The displays threw off enough energy near the rx freq to cause the site radio to go deaf. It was broadband noise with a spur that landed almost on freq so that even if they elected to apply for a new freq license, they would still get some interference from the displays. Since the radios are housed in the panel cabinet inches away from the back of the display, there wasn't anything we could do about it except to put a power switch on the displays to kill them when no one was on site.

I've had surveillance cameras throw off noise that interfered with UHF. I've had routers, PC's, PLC panels, ethernet cables, wi-fi outdoor units mounted on the antenna mast, telephone switches, and telephone desksets all cause interference. It always required I move the radio and/or the antenna someplace quieter.

You can determine this by doing a receiver desense test, and then systematically turning other things off. You'll need an experienced tech and a service monitor to do the work.

[emtprt]

The issue ended up being a bad tone remote, not interference as initially diagnosed. F1 on console into control station worked fine but when channel changed to F2 only able to TX no RX into console.
Tone remote being replaced.
Thanks