Search found 9 matches

by Steve Brown
Wed Feb 21, 2018 5:10 pm
Forum: FM Radio
Topic: Harris FM-25K issue
Replies: 16
Views: 1446

Re: Harris FM-25K issue

Glad to hear that you found your problem, which wasn't anything most of us suspected. I'm curious about one thing, though. On Continental/Collins FM transmitters a quick easy way to drop power is to trip off the screen breaker, which lowers the output to around 15% of normal. In those rigs that does...
by Steve Brown
Wed Jan 24, 2018 3:32 pm
Forum: FM Radio
Topic: Connector suppliers....
Replies: 14
Views: 721

Re: Connector suppliers....

Pasternack has a whole series at this link---not cheap, but...

https://www.pasternack.com/nsearch.aspx ... _type=grid
by Steve Brown
Wed Jan 10, 2018 7:28 pm
Forum: AM Radio
Topic: What is this? A 5 kw Dummy Load or what?
Replies: 22
Views: 3017

Re: What is this? A 5 kw Dummy Load or what?

An old TV engineer once showed me a 'whiskey cup', which was an adapter for the center conductor of 51.5 ohm line to make the transition to the 'new' standard of 50 ohm line.

Steve Brown
by Steve Brown
Mon Nov 06, 2017 9:31 am
Forum: FM Radio
Topic: Harris FM-25K issue
Replies: 16
Views: 1446

Re: Harris FM-25K issue

I found a Harris tech note that talks about failures of the module, which is a low pass filter and directional coupler combined. They say to look at variable caps C1 and C3 for clear glass, which means OK---dark glass means failure. Since the device is 50 ohms in and out, you can just terminate the ...
by Steve Brown
Mon Nov 06, 2017 9:09 am
Forum: FM Radio
Topic: Harris FM-25K issue
Replies: 16
Views: 1446

Re: Harris FM-25K issue

You should check the components in the directional coupler box, the one that lives between the IPA and the cable that connects to the PA cavity. Minnesota Public Radio had a similar issue a few years back and thought like you did that the problem was a faulty cable connection. As I recall, Harris co...
by Steve Brown
Wed Sep 27, 2017 4:41 pm
Forum: Ask the Engineers
Topic: Source needed for a few misc parts:
Replies: 4
Views: 547

Re: Source needed for a few misc parts:

Chuck, I have a similar meter, but if may be a sacrilege in a Collins rig---it's labelled "RCA" on the bakelite. It's got a shunt on it that makes the meter read 1 amp DC full scale, and the meter scale reads 0 to 1 amp. The meter itself is 2-3/4" in diameter. If you're interested let me know and I'...
by Steve Brown
Sat Aug 12, 2017 6:30 pm
Forum: FM Radio
Topic: Harris HT30 issue
Replies: 10
Views: 1453

Re: Harris HT30 issue

I'll second the comments about the auxiliary contacts on the high voltage contactor. The current through those contacts is very low, and if the status input it drives isn't satisfied then the transmitter drops off or overloads. I put a pull down resistor between the status input for those contacts a...
by Steve Brown
Fri Jun 23, 2017 10:07 am
Forum: AM Radio
Topic: Daytime Impedance high?
Replies: 26
Views: 3460

Re: Daytime Impedance high?

Fossil and anyone else who might be interested. Contract engineer Doug Thompson knows where there are at least four of the Harris sliding motorized contactors that were replaced with Kintronics contactors some years ago. The Harris contactors didn't seem to want to slide well in cold weather here in...
by Steve Brown
Tue Feb 21, 2017 4:29 pm
Forum: FM Radio
Topic: Z 10 rigs
Replies: 4
Views: 794

Re: Z 10 rigs

Rich, you might want to contact engineering at Minnesota Public Radio. When we converted some of their Z transmitters to HD radio the old analog modules got pulled and the new linearized modules were installed, and I think they hung onto the analog modules--they should have a bunch of them. The Othe...