Search found 49 matches

by DaveSt
Sun Sep 08, 2019 1:13 am
Forum: FM Radio
Topic: Quick STL Question
Replies: 6
Views: 608

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: 332

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: 527

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: 527

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: 978

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: 9
Views: 364

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: 356

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: 406

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.
by DaveSt
Wed Jul 03, 2019 11:49 pm
Forum: Everything else
Topic: Which Android App to Record Interview directly on phone?
Replies: 2
Views: 188

Re: Which Android App to Record Interview directly on phone?

The Tieline Report-IT app can be used for recording. Obviously they would like you to buy one of their codecs for the live side, but the recording bit is free as I recall. http://tieline.com/products/G5/Report-IT
by DaveSt
Wed Jul 03, 2019 3:13 pm
Forum: Everything else
Topic: What's with all the spam lately?
Replies: 6
Views: 145

Re: What's with all the spam lately?

Probably the moderator(s) are busy earning money in their day job rather than sitting in front of a computer all day to catch the spam as it appears. To me the amount of spam here is not bad and is easily ignored as it is so obvious. It usually gets killed within a day or so anyway.
by DaveSt
Mon Jul 01, 2019 9:23 am
Forum: FM Radio
Topic: 75 uSec Pre-Emphasis Graph
Replies: 11
Views: 469

Re: 75 uSec Pre-Emphasis Graph

There are some very simple browser based circuit simulators. For example https://www.circuitlab.com/ . For pre-emphasis you can do a parallel RC combination into the non inverting input of an op-amp. If you have the circuit of the pre-emphasis part of whatever box you have, you can simulate it exact...
by DaveSt
Thu Jun 06, 2019 5:35 am
Forum: FM Radio
Topic: Changing Frequency Of Belar RFA-1 FM RF Amplifier
Replies: 6
Views: 357

Re: Changing Frequency Of Belar RFA-1 FM RF Amplifier

I would have thought the front end and LO coils would have the range for the whole of the FM band. As Deep Thought said, it is a simple circuit and retuning should not be a challenge for any one with a little experience.
by DaveSt
Mon Apr 15, 2019 9:53 am
Forum: Ask the Engineers
Topic: Audio dropouts on Yankees game broadcasts
Replies: 34
Views: 1479

Re: Audio dropouts on Yankees game broadcasts

13dB is very good, so no problem there. $5000 for one of these boxes sounds like more than double what it should be, unless it is gold plated. I am going to guess the carrier is DVB-S QPSK 3/4. So you could put just about any other receiver on that with a splitter, even a domestic receiver and see i...
by DaveSt
Mon Apr 15, 2019 1:22 am
Forum: Ask the Engineers
Topic: Audio dropouts on Yankees game broadcasts
Replies: 34
Views: 1479

Re: Audio dropouts on Yankees game broadcasts

It looks like your downlink frequency is 4029MHz based on the IF frequency shown by your receiver. That is good as interference problems are more of a problem at the lower C-band. The filter on the feed itself may be from someone like MFC. These filters became very popular for getting rid of interfe...
by DaveSt
Fri Apr 05, 2019 3:08 am
Forum: STL Engineering
Topic: RDS options
Replies: 15
Views: 741

Re: RDS options

There is a document that covers this from the RDS Forum. It is old, but still relevant: http://www.rds.org.uk/2010/pdf/R09_048_6_no%20pw_57.pdf . The important bits are highlighted on page 4. Page 40 of the NRSC guidelines also has some information on page 40: https://www.nrscstandards.org/standards...