Batboard

Hi,

When programming a radio for a friend yesterday we noticed that something seemed to be interfering with one channel we were on. I then added a DPL and the radio worked fine until about an hour later when he came back to me with the problem. I tried putting the DPL in again with no luck. The strange thing is that my other radios do not pick this interference up. Also, when I connect the speaker microphone it some how increases the interference where there is none. Has anybody ever seen this before if so have you fixed it?

The radio is a Motorola HT1250 "S" split.

Model: H25SDF9AA5
Serial: 749TLY0353
Version: R05.16.01

-Jeff

Hi,

Can you tell us what frequency is that you are having a problem with? You may be picking up a birdie (spurious emission) from the radio itself. The birdie may be from a parasitic oscillation in the radio, or it could be a mixing product from the radio's internal clocks and oscillators. It's possible that the birdie could be radiated from the microphone cord. Do you hear it on another radio if you hold the other radio near the one with the problem?

If you tune another 1250 to the same frequency, do you hear anything? If it affects more than one radio of the same model, then you likely have an internal mixing product problem. What happens if you remove the antenna on the offending radio?

PL

The frequency is 470.400 mhz with a dpl of 251. I do not receive the signal on another radioradio when it is next to it , and it wont receive it without an antenna. I do not have another 1250 in that range I can place next to it. Also, I notice that the interference occurs when the radio is on scan probably indicating something internal.

Thanks,

Jeff

Can you tell us the firmware revision that's currently installed in the HT

Al wrote:Can you tell us the firmware revision that's currently installed in the HT

Version: R05.16.01

Does anybody have a solution for this? If not should I send it back to Motorola it is still under warranty?

When I worked for Harris RF Communications back in the dark ages, we knew what birdies existed on what radios. Have you contacted Motorola and inquired if there is a known problem with the radio on that frequency?

On the XTS series, I believe there was an option somewhere in the CPS that had something to do with the 2nd local oscillator. Never goofed around with it, but I suspect that it had something the do with changing the LO to move birdies out of the IF passband? Don't know if there is such an option in the HT 1250? Anyone else got an idea? I don't know the 1250 well, but I've chased RF birdies in the past.

If the radio is under warranty, you may as well send it in. Good luck. It never fails that some offending parasitic ends up on one of your frequencies, but with so many CPU clocks in everything around us, it's not surprising. Good luck!

-PL

Thanks I will contact Motorola later today.