Search found 3187 matches

by Deep Thought
Mon Nov 13, 2017 5:40 pm
Forum: Ask the Engineers
Topic: FAA requirements for Decommissioned towers
Replies: 5
Views: 198

Re: FAA requirements for Decommissioned towers

Yeah, some asshole inspector wanting to make trouble for someone will nick you for not notifying the FCC about a dismantled tower (or one registered but not constructed). Definitely go into the ASRN system and change the status to "horizontal". :) As for the FAA, you file a 7460-2 Supplemental Notic...
by Deep Thought
Mon Nov 13, 2017 5:30 pm
Forum: STL Engineering
Topic: Aligned our STL this morning. Opinions?
Replies: 8
Views: 285

Re: Aligned our STL this morning. Opinions?

26 dBu (19 uV) is pretty miserable. You've got something horribly wrong unless this is a 20 mile hop, and even then the received signal levels should be at least an order of magnitude better.
by Deep Thought
Mon Nov 13, 2017 5:27 pm
Forum: FM Radio
Topic: FM range question - coastal mountainous terrain
Replies: 22
Views: 677

Re: FM range question - coastal mountainous terrain

Could you be so kind as to do that again for say 4kW in the same location, for 4 antenna bays instead of two, and for both those combined 4Kw + 4 bays? Mr. Fry will probably answer you directly, but as a practical matter the number of bays is irrelevant, and the increase from 1 to 4 KW will just do...
by Deep Thought
Sun Nov 12, 2017 9:31 pm
Forum: Ask the Engineers
Topic: Convert to LEDs, or leave 110v?
Replies: 7
Views: 219

Re: Convert to LEDs, or leave 110v?

Why not just use a commonly available 110v. LED bulb screws right into your existing socket. Exactly. A 20 watt equivalent LED directly replaces this for $5. https://www.amazon.com/B2ocled-2-Pack-E26-LED-Bulb/dp/B01MFDF3R7/ref=sr_1_11?s=hi&ie=UTF8&qid=1510543834&sr=1-11&keywords=3+watt+led+bulb
by Deep Thought
Thu Nov 09, 2017 8:18 pm
Forum: FM Radio
Topic: FM range question - coastal mountainous terrain
Replies: 22
Views: 677

Re: FM range question - coastal mountainous terrain

Ha! I keep forgetting that's in Google Earth. Yeah, that's going to be nearly impossible to blast through. Best advice would be to find some midpoint along the coast that can "see" both areas to put up a booster aimed to the shadow area if those are allowed over there.,
by Deep Thought
Thu Nov 09, 2017 9:56 am
Forum: FM Radio
Topic: FM range question - coastal mountainous terrain
Replies: 22
Views: 677

Re: FM range question - coastal mountainous terrain

Can you see the target area from the transmitter site? If not, there is little you can do to get past the terrain obstruction other than raising the antenna higher. "we need to roughly double our range in that direction" All else being equal, on flat terrain the 60 dBu contour of a station running 1...
by Deep Thought
Wed Nov 08, 2017 6:16 pm
Forum: FM Radio
Topic: OMB PTX-20 test and repair help required
Replies: 15
Views: 411

Re: OMB PTX-20 test and repair help required

10 to 15 miles is about right for a 1 KW station assuming that the antenna isn't very high off the ground.
by Deep Thought
Tue Nov 07, 2017 9:36 pm
Forum: FM Radio
Topic: OMB PTX-20 test and repair help required
Replies: 15
Views: 411

Re: OMB PTX-20 test and repair help required

Attach a proper dummy load and turn the RF level all the way down. If it stays on then gradually increase the power, watching the meter. This is only a 20 watt transmitter so a power draw of less than 100 watts would be expected.
by Deep Thought
Tue Nov 07, 2017 10:39 am
Forum: FM Radio
Topic: OMB PTX-20 test and repair help required
Replies: 15
Views: 411

Re: OMB PTX-20 test and repair help required

This is the same unit as a Bext PTX-20. Unfortunately, it is rather old and Bext and OMB aren't terribly good about supplying manuals. "AJ POT" is RF output level. "AJ DESV" is deviation (modulation) adjustment. The 50 watt scale is for measuring forward power while the 5 watt is for low forward pow...
by Deep Thought
Mon Nov 06, 2017 12:05 pm
Forum: FM Radio
Topic: Nautel NV20 repair/restoration
Replies: 16
Views: 1170

Re: Nautel NV20 repair/restoration

That was...amazing.

Not to be a Nosy Nellie, but what value would you put on this repair? I know it'll be significantly less than what a new transmitter costs, but I collect these figures for insurance estimation purposes during post-mortem inspections.
by Deep Thought
Mon Nov 06, 2017 11:49 am
Forum: FM Radio
Topic: Harris FM-25K issue
Replies: 10
Views: 329

Re: Harris FM-25K issue

"Don't trust the BW reflectometer". Indeed. I had one of their 600 watt transmitters practically burn itself up because the reflected power sensing did not work at all. I did a similar conversion on a FM25K, feeding it with a Nautel VS300. One thing to make sure of is that you are only feeding enoug...
by Deep Thought
Thu Nov 02, 2017 11:50 am
Forum: FM Radio
Topic: OMB GP-6
Replies: 11
Views: 450

Re: OMB GP-6

Without knowing the power split between bays or the normal bay impedance this is going to be a blind walk down a tightrope. However, you should be able to get some kind of an idea of the health of the thing by measuring one bay at a time. It probably won't be 50 ohms because the other five aren't pa...
by Deep Thought
Thu Nov 02, 2017 8:38 am
Forum: Ask the Engineers
Topic: What might this unit be for?
Replies: 6
Views: 292

Re: What might this unit be for?

Labels are just a convenient way to containerize things we can't control. :mrgreen:

I've seen similar things which were merely remote meters, but this one seems to be more 3D than those.
by Deep Thought
Wed Nov 01, 2017 8:44 pm
Forum: Ask the Engineers
Topic: Will this STL link work?
Replies: 3
Views: 143

Re: Will this STL link work?

That looks like it is 2.4 or 5 GHz. I ran the path study for him and at 950 it's a lot "fatter" at 60%, but only loses 4.5 dB because of it.
by Deep Thought
Tue Oct 31, 2017 8:30 pm
Forum: Ask the Engineers
Topic: What might this unit be for?
Replies: 6
Views: 292

Re: What might this unit be for?

That is almost certainly a homebrew modulation monitor.