Oh my, our 60 dbu contour covers about 93,000 people
Thats LPFM for you Sounds like we're gonna have a really good time with this.
As mentioned, you may want to consult with Nautel, but in theory, as long as your transmitter/Power Amplifier is wideband enough and with enough headroom, you could probably low-level combine the analog and HD into a single amplifier/transmitter. You would have to add some pretty steep RF filters on the output, and replace your existing antenna with a high quality commercial broadband antenna. The station would have to also purchase and install the more expensive exciter, exporter, and pay Ibiquity fees. No matter what your class of station, HD is a steep capital expense.
There are several possible methods for producing an HD signal. One is low level combining which has already been covered pretty well. An alternative is to use an HD transmitter to feed a separate antenna. Sometimes, this is more cost effective, depending upon your circumstances.
Something also to think about is that LPFM stations can own up to two translators. One or both could rebroadcast HD signals, thus expanding the program offerings of the LPFM.
I did get lots of good info from Nautel. We can do it from the transmitter and their exciter importer and exporter is ready made for the transmitter we have. I already have the quotes and set as far as that. The transmitter is adjacent to our studio, so no STL concerns. The need for added RF filter is new to me (thank you).
The problems as I see it, from a novice perspective, is the TPO headroom isn't there for a single bay antenna. The antenna is also very narrow band so real changes will have to made there and two bays will be needed. Jampro is another great bunch of folks they're setting up the antenna system to be HD friendly.
This juuuust might work
I guess I should add: The whole antenna system has to fit on a 2" pipe mast on our roof. So we're fairly limited as to space. We can have a 1/2 spaced two bay with a low physical profile -- no tower -- this is LPFM all the way
Last edited by Ralph Martin; 12-19-2016 at 01:28 AM.
Thanks for that, Kmagrill -- I'm sure you're right, but I hope I can get the JLCPs to work because they have such low wind drag and the mast can't be guyed. But, alas; physics is physics...
I'm going to miss the single bay match we get. It's so good that I'm sceptical of the readings (less than 1 watt reflected with 274 forward). That's of course, unless a good sized bird decides to sit on the antenna for a little rest and ruin the match enough to cause a power foldback. Caught the big guy landing and sure enough, I get a SWR power foldback alarm on my phone. He takes off and everything's back the normal. I'm told a 2-bay won't be so affected by birds. Wow! Something to look forward to already
Just some thoughts, as I catch up on a couple months worth of traffic.
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Unfortunately the vs1 isn't LPFM certified -- only their vs300, so we're limited in that way. The good thing is that the cost of adding a second element won't be much because we just have in on a mast. It just requires the purchase of the antenna and combiner... oh, and a good a-frame ladder. That, I hope will bring the TPO needed down to 170 watts. With a single bay, I might be able to get -18dBc that won't do it for us. My goal is -14dBc. With a vs300, I'm gonna need a 2-bay and their "power-boost" addition.
My big challenge right now is making sure the antenna system will tune wide enough (200kHz each side). Jampro is still working out the details for me. I should know more this week.
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