Search found 56 matches

by DaveSt
Wed Apr 29, 2020 7:40 am
Forum: FM Radio
Topic: Digit or Digit-CD full manuals
Replies: 28
Views: 1268

Re: Digit or Digit-CD full manuals

kcbooboo wrote:
Wed Apr 29, 2020 5:20 am
Thanks for the suggestions.

I think that "B [2/A7]" is just another place that uses that bias voltage.
Yes it is the other half of the U20 comparator IC. You could swap the IC out too. Your idea of tying the input to 5V is a good way to go.
by DaveSt
Tue Apr 28, 2020 11:58 pm
Forum: FM Radio
Topic: Digit or Digit-CD full manuals
Replies: 28
Views: 1268

Re: Digit or Digit-CD full manuals

From the schematics that were linked earlier, have a look at page 19. That shows the circuit for the RF mute input. You could try checking the components connected to that. Particularly R3, R30, CR1, C5. Also monitor the voltages around U20 and at TP4 during the good and fault conditions. The fault ...
by DaveSt
Sun Mar 08, 2020 11:29 am
Forum: STL Engineering
Topic: Barix Audio Issue
Replies: 10
Views: 349

Re: Barix Audio Issue

Try swapping out the power supplies.
by DaveSt
Fri Feb 28, 2020 12:26 am
Forum: Production Studios
Topic: Small and robust sound card. Recommendation?
Replies: 2
Views: 1192

Re: Small and robust sound card. Recommendation?

For a card, have a look at the Sonifex PC-AD2. It is not cheap at around $700, but is fully balanced. Or for a USB device, the Yellowtec PUC2 is good.
by DaveSt
Mon Jan 06, 2020 1:54 am
Forum: FM Radio
Topic: Smart AC Power Circuit Breaker with Web Control?
Replies: 18
Views: 784

Re: Smart AC Power Circuit Breaker with Web Control?

The old panel box is about 40 years old. I would never want a circuit breaker that I can't reset in person. If something causes a trip, you're not sure, hit "reset", and it comes back, you could be looking at replacing the panel with the rest of the building that burned down. For the nuisance for a...
by DaveSt
Fri Dec 06, 2019 12:05 pm
Forum: FM Radio
Topic: Wind Farm
Replies: 6
Views: 838

Re: Wind Farm

As far as wind turbines go, the support structure is steel and represents a permanent reflector, but as Deep Thought suggests, that is probably a minimal problem if many wavelengths away. Of course, FM is not analog TV, but I know of one instance where a tower caused a permanent reflection (ghost) ...
by DaveSt
Mon Nov 25, 2019 11:36 pm
Forum: Radio Studio Engineering
Topic: Soundcraft RM100 tech manual
Replies: 2
Views: 897

Re: Soundcraft RM100 tech manual

I also have an electronic version of the technical manual. Let me know if you want it. It is just under 9MB.
by DaveSt
Sun Sep 08, 2019 1:13 am
Forum: FM Radio
Topic: Quick STL Question
Replies: 6
Views: 863

Re: Quick STL Question

Keep in mind that a lot of the older Marti and other STL transmitters use RF modules that are unobtainium. Often another available module will work at lower power but I haven't had real good luck long term with those conversions. Additionally, some of the Marti receivers have VCO (IIRC) modules tha...
by DaveSt
Tue Aug 27, 2019 9:17 am
Forum: FM Radio
Topic: Optimod 2300 Tally Output to Sine RFC-1/B
Replies: 3
Views: 482

Re: Optimod 2300 Tally Output to Sine RFC-1/B

The NPN output transistor in the Optimod has its emitter connected to ground (pin 1). So you can use the collector which is the actual output to control anything so long as you stay within the current and voltage rating of the transistor. You can use a resistive potential divider so that you can pul...
by DaveSt
Tue Aug 27, 2019 12:44 am
Forum: FM Radio
Topic: FM Antenna Tuning
Replies: 11
Views: 873

Re: FM Antenna Tuning

If the filter is not inline, then it could have been removed because it makes the VSWR problem worse. That does not necessarily mean the filter is not correctly tuned as changing the length of the feeder will affect the VSWR shown at the transmitter. If you are getting enough RF from the other trans...
by DaveSt
Mon Aug 26, 2019 2:48 pm
Forum: FM Radio
Topic: FM Antenna Tuning
Replies: 11
Views: 873

Re: FM Antenna Tuning

You would certainly want all transmitters any where near that system to be off before you connect your spec analyser to the system. Test with plenty of attenuators first. Without knowing some details of the antennas, it is hard to comment further. You might have an issue that is not down to tuning o...
by DaveSt
Thu Aug 01, 2019 2:26 pm
Forum: Radio Studio Engineering
Topic: Arrakis ARC-10 USB Noise
Replies: 9
Views: 1615

Re: Arrakis ARC-10 USB Noise

Finding a decent professional USB audio interface is not easy. One I have used with good results is the Yellowtec PUC2. It is 2x USB powered, so does not achieve the high levels of the Henry box, but a good choice if you want something USB powered. Like the Henry, it does not have any knobs or butto...
by DaveSt
Wed Jul 17, 2019 11:34 pm
Forum: FM Radio
Topic: Exciter shopping
Replies: 15
Views: 1096

Re: Exciter shopping

Personally, I am not a fan of the FX-50. You could add the GatesAir Flexiva Compact which has a 50W version to your list. Not cheap, but very good. You might be lucky and find something used.
by DaveSt
Tue Jul 16, 2019 11:24 pm
Forum: Ask the Engineers
Topic: Cutting Hard Line
Replies: 12
Views: 540

Re: Cutting Hard Line

I have seen all sorts of tools used and I have come to the conclusion that so long as you get the end square and clean and clear out the dust it does not matter how you do it. A band saw sounds reasonable to me. I hope the install goes well, the FAX is a good transmitter in my experience.
by DaveSt
Sat Jul 13, 2019 2:39 am
Forum: FM Radio
Topic: Harris Z FM FET replacement
Replies: 7
Views: 595

Re: Harris Z FM FET replacement

There is some calibration needed, not least of which is the bias. It is better to send it back rather than risk killing expensive MOSFETs.