Search found 76 matches

by ncradioeng
Wed Jan 15, 2020 10:23 am
Forum: AM Radio
Topic: Gates 5--no audio
Replies: 28
Views: 1242

Re: Gates 5--no audio

There are two amps on the PDM amp board - they can be independent or paralleled depending on the jumper position. Moving the jumper to the 1kw position to get audio is a clue.
by ncradioeng
Tue Jan 14, 2020 10:44 am
Forum: AM Radio
Topic: Gates 5--no audio
Replies: 28
Views: 1242

Re: Gates 5--no audio

I wouldn't rip out those IC's until more troubleshooting is done. What does the waveform output look like with the cable disconnected? Could be a problem with the PDM amp inputs. Give this guy a call - he's pretty good at keeping those things going: http://michaelpatton.com/transmitters/ He may have...
by ncradioeng
Mon Jan 13, 2020 10:56 am
Forum: AM Radio
Topic: Gates 5--no audio
Replies: 28
Views: 1242

Re: Gates 5--no audio

According to the manual, you should have 13-14 Vp-p square waves coming out of the PDM generator.
by ncradioeng
Sat Jan 04, 2020 8:46 am
Forum: FM Radio
Topic: How to feed mono only audio into base band input on tx?
Replies: 14
Views: 416

Re: How to feed mono only audio into base band input on tx?

Car radios use a technique called "blend". As a stereo signal gets weaker (and noisier), the radio will blend to mono (as opposed to a hard switch) to reduce the noise from the L-R subchannel. L / R separation diminishes in the process.
by ncradioeng
Fri Jan 03, 2020 11:11 am
Forum: FM Radio
Topic: How to feed mono only audio into base band input on tx?
Replies: 14
Views: 416

Re: How to feed mono only audio into base band input on tx?

You need some sort of audio processor with a limiter to have a decent loudness level while preventing overmodulation. I would get a used FM Optimod or equivalent and set it to run in mono. Most of them take the left channel audio input as the mono input. When used this way, the composite output stil...
by ncradioeng
Thu Jan 02, 2020 3:39 pm
Forum: FM Radio
Topic: How to feed mono only audio into base band input on tx?
Replies: 14
Views: 416

Re: How to feed mono only audio into base band input on tx?

The audio will need 75-us pre-emphasis if your processor doesn't provide it. The MPX input normally has a flat frequency response. If you connect it up and it has no high-end response, then that would confirm it.
by ncradioeng
Thu Jan 02, 2020 8:41 am
Forum: AM Radio
Topic: Gates 5--no audio
Replies: 28
Views: 1242

Re: Gates 5--no audio

The four PDM outputs from the generator board should be square waves that change width with audio and power level adjustment. The outputs are displaced by 90 degrees from each other - hence the term "polyphase".
by ncradioeng
Sat Dec 28, 2019 2:22 pm
Forum: FM Radio
Topic: Nicom BKG77 Issue I think
Replies: 11
Views: 579

Re: Nicom BKG77 Issue I think

I had a new two-bay Nicom BKG77 that would intermittently short out and shut down a Nautel. It finally stayed shorted long enough to find out that the power divider was the culprit. We took it apart and discovered that a jam nut on the center feed at the input end was contacting the case. Turning th...
by ncradioeng
Fri Dec 20, 2019 8:55 am
Forum: AM Radio
Topic: AM Digital NPRM
Replies: 54
Views: 2384

Re: AM Digital NPRM

Does all-digital do stereo?
by ncradioeng
Fri Dec 13, 2019 10:11 am
Forum: AM Radio
Topic: AM Digital NPRM
Replies: 54
Views: 2384

Re: AM Digital NPRM

They can do it because the audio is digitized and processed (i.e. compressed) down to a bit rate that fits in the 10 kHz wide slot. Just like OTA HDTV and mp3's.
by ncradioeng
Mon Dec 09, 2019 9:30 am
Forum: AM Radio
Topic: How do the AM pros do this?
Replies: 10
Views: 630

Re: How do the AM pros do this?

Wind your own isolation choke with some Cat5 similar to the lighting choke link below. Don't use the capacitors on each end of course. Two or three inch PVC should work for the form.

https://www.kintronic.com/shop/lighting-choke/
by ncradioeng
Wed Sep 25, 2019 2:45 pm
Forum: TV Engineering
Topic: TV OTA antennas
Replies: 9
Views: 709

Re: TV OTA antennas

Just saw off the last three or four directors.
by ncradioeng
Tue Jul 30, 2019 3:18 pm
Forum: FM Radio
Topic: Continental 816-R2 air chimney screws
Replies: 5
Views: 250

Re: Continental 816-R2 air chimney screws

I'm using the nylon thumbscrews (I think I got them from Lowes in the specialty hardware section). So far they seem to be working. Beats fiddling with a screwdriver since you have to install the rear ones by feel.
by ncradioeng
Thu Jul 18, 2019 11:33 am
Forum: Ask the Engineers
Topic: Cutting Hard Line
Replies: 12
Views: 456

Re: Cutting Hard Line

I've used a hose clamp as a cutting guide and a fine-tooth hacksaw. Takes a little time, but if you're only doing a couple of cuts, it works OK.
by ncradioeng
Mon Jul 08, 2019 3:02 pm
Forum: AM Radio
Topic: BE AM-6A RF Out Problem
Replies: 19
Views: 928

Re: BE AM-6A RF Out Problem

If the top PA power supply isn't working, the transmitter will not come on. BTDT. I can't remember if one of the fuses was blown associated with that power supply or what, but there were no faults showing and I was going in circles until B-E made the comment concerning the situation with that supply.