I could use your thoughts on this. I help out with the electronics at a large annual one-day garage sale for Habitat for Humanity. We get a lot of TVs donated. We're taking steps to accept fewer of them and market the ones we get a little better. One thing is to get them playing.

I was thinking of a distribution amp or modulator (Blonder Tongue Agile like the AM 60-450) or I found a Holland Modulator on ebag as well. These have coax 75 ohm output which I can split to run several sets. People say online that they have enough RF output power to run several TVs at once.

My problem is with the inputs. The BT has an RCA audio input jack and a 75 ohm video input. I can't figure a simple way to feed both of these. If we use a DVD player it will have analog R/L audio and composite video outputs - no 75 ohm RF video output. I could use an antenna and get local OTA HDTV, but then I'd need a converter box (these are tube type TVs). That would give me analog channel 3 over a 75 ohm coax, but how do I feed the analog audio input on the BT?

The Holland (HPM55) has 75 ohm coax inputs for both audio and video - gack - ?! No idea how to feed audio to that input. There aren't good manuals out there for this gear, I think the CATV pros just knew what they were doing and had the right eqpt to feed these.

I'm thinking maybe I should abandon the pro gear and just get a cheap consumer grade distribution preamp. I just don't trust the quality of mass produced junk with those cheap little wall warts.

Suggestions welcome.

I suspect that you just need an RCA to f or RCA to bnc adaptor... the BT video input is for baseband video , not rf... the outputs from a dvd player should work fine.
http://www.amazon.com/C2G-Cables-Go-27312-Adapter/dp/B0002J25OI/ref=sr_1_1?ie=UTF8&qid=1457737437&sr=8-1&keywords=rca+to+f+type

http://www.amazon.com/Monoprice-BNC-Male-Female-Adaptor/dp/B006VK8IEI/ref=sr_1_5?ie=UTF8&qid=1457737377&sr=8-5&keywords=rca+to+bnc

jr

OK if you need RF to the TV's use:
A DVD player into an RF modulator ( unless its a rare DVD w/RF out)
then into a DISTRIBUTION RF amp then multi set couplers.

If the TV's have A/V ins use DVD then A/V distribution amp, the
ones I have seen have multiple outputs.

Alternative is use a good modulator, cut a dipole for its output
& hang some sort of wire off the TV's RF in. At close range should work good.
Others do it for whole house coverage & probably next door.
Dont tell the FCC !

73 Zeno:smoke:

My problem is with the inputs. The BT has an RCA audio input jack and a 75 ohm video input. I can't figure a simple way to feed both of these. If we use a DVD player it will have analog R/L audio and composite video outputs - no 75 ohm RF video output. I could use an antenna and get local OTA HDTV, but then I'd need a converter box (these are tube type TVs). That would give me analog channel 3 over a 75 ohm coax, but how do I feed the analog audio input on the BT?

The Holland (HPM55) has 75 ohm coax inputs for both audio and video - gack - ?! No idea how to feed audio to that input. There aren't good manuals out there for this gear, I think the CATV pros just knew what they were doing and had the right eqpt to feed these.


Both modulators should accept the same A/V signals (Yellow/White/RED RCA jacks) that any DVD player, VCR, DTV converter box, etc. put out. The only MINOR issue is that the connector jacks are different (Jr_tech posted the default solution). No need to connect both audio outputs to the audio input of the of whichever modulator you choose (either one will do), but if you feel better using both then get an RCA Y cable (RCA spliter/combiner) and use that to mix your stereo audio down to mono.

http://www.hollandelectronics.com/support/_manuals/head_end/HPM55_PM.pdf

I think in a garage sale scenario no one will give you grief about monitoring only one audio channel. Using a y-cable as a combiner is just the same as connecting the output of one channel to the output of another... not good electronically or (usually) sonically. :nono: They're splitters, not combiners or mixers.

Chip

If you need a DVD player with RF out, use a combo DVD player/VCR. Every one I have seen can output composite video, stereo audio and RF simultaneously.

Will your customers be confused when they get home and the set won't work? :scratch2:

A little slow on the response here but thanks for all the advice. I think I can figure out something that will work now.

Will your customers be confused when they get home and the set won't work? :scratch2:

I don't see how that would happen. Everyone pretty much knows you need an adapter box to watch DTV nowadays. Actually a lot of the sets that sell are to people doing gaming. One of our criteria to accept donated TVs is that they have AV input jacks to allow for connecting game consoles.

Keep in mind that in the later years of CRT TV production, there were sets with both a CRT display and an ATSC tuner. Look for a "DTV", "SDTV", or "ATSC" logo on the front (NOT "HDTV ready"). We have three CRT sets working from an attic antenna. Make "no cable needed" a selling point.

Great idea, thanks!

Thought I'd give an update on how this worked out. I bought 2 Blonder-Tongue Agile Modulators off ebay, pretty cheap (I think about $50-$60 for both with shipping). Unfortunately they arrived the DAY OF the sale - should have bought sooner.

This sale is so big we have to set things up, test and price items days and evenings before the sale. We ended up getting several converter boxes donated, and I was able to set up a couple banks of 2-3 sets running off a converter with splitters. Signal strength was not too great due to the concrete block building and splitting the converter box output, so we had some pixellation, but it was still much better than no picture at all in terms of sales. We sold about 10 TV's compared to about 2 last year. Combined with some new rules limiting donations to working TV's with A/V inputs and remotes, we only had 2 small TV's to discard and 4 working ones left after the sale that went over to the Habitat Restore for sale there. I considered it a great success.

Next year we'll be ready with the modulators and if I ever get any vintage TVs working for my own collection, I'll have them handy for that.

Thanks again for all the advice.