My new Blonder Tongue AM40-550!
 

On Sunday, I ordered this off eBay for $25. I plan to use it to broadcast to the 1960's color console TV that I still don't have. I drew out a plan for rearranging my bedroom with the new TV receiving all the cable and DVD stuff through UHF. I'm going to Radioshack tomorrow to get the F to RCA adapter for the video in.

Words of advice: If you use UHF first use a DTV box with a signal meter (like a Zenith DTT901 in the menu's manual tune mode) to find all receivable and too-weak to receive DTV carriers (I made a list of all active carriers and their channels) and select a channel that is unoccupied and has at least one unoccupied channel on either side of it (not always easy on UHF)....If you don't you will get interference (out shouted if on the same channel, or otherwise adjacent channel) from OTA DTV stations. The transmit antenna you use is CRITICAL to performance. Shango66 has a good youtube video on custom making a good one (I lack the SWR meter so I fine tune by rough guess), but UHF antennas are too short to use that technique accurately without an SWR meter.

The AM40 series can muster about 60-100' of transmission range (before complete snow-out) under optimal circumstances, if you wish to cover your whole house/yard snow free you want an AM60 or BAVMz series.

Unless you have a LOT of TVs, TVs in several rooms, or portable sets it is usually cheaper and easier to get a generic ch 3/4 modulator or VCR with one builtin and go with a wired interconnect system...I had 7 sets that would get used on a wired system in one room till I moved and wound up with 5 in one room (main signal source cluster), 7+ in another, and over 30 in the basement....At that point the amount of wire spliters and modulators to make that all work was more expensive than a good BT modulator or three, and a change in strategy was made.

You could use a UHF channel above channel 52. You should be clear of any current DTV stations. You might get some interference with cell phones, but unless the cell tower is next door, this shouldn't be a big issue.

You can also go to tvfool.com to confirm what UHF channels are used in your area. That modulator will only go up to UHF channel 26 (just below 550 MHz, the "550" from its model number), so your choice must be within that range.

In addition to the 550 series being limited to ch 26 there is also the issue of having plenty of VHF only sets....I don't want each one tethered to a modern VCR or the like, and of the 5 vintage UHF converters I've had not a damn one has worked (even with recaps)...I'm thinking of gutting some to use a project boxes.

Whatever I do, I cannot get this thing to work on VHF. Despite seeing other people do it on Youtube. Ideas?

The antenna is critical, and this video is my guide. https://www.youtube.com/watch?v=z4dhRt7tmd4 I don't have an SWR meter like he does so I take the percentage of length he shaved and apply it to the antenna I've made for any given channel.

Make sure the output level screw pot is at max (you've got one of the weaker models so even at max it's range won't be great).

Make sure your channel set dip switches are correctly set.


Does it output on any channel?...I've bought defective ones that the seller claimed to "work" before, and had good ones die.

Most Blonder Tongue modulators are most powerful on channel 7 VHF (several modulators I've had exhibit this, and I know someone else that has observed the same thing with his BT rig).

The metal and human body can cause reflections and block signal so having a portable battery operated set to test your range and signal conditions in the areas you plan to use it is sort of a must.

Make sure it is set for the off the air channel assignments: these things
can use cable channel assignments.

I decided that I wanted to use this thing on channel 6 VHF so I could also pick it up on the FM dial. Mind you, I only want to be able to transmit about 10 feet with it. I found a guide for VHF antenna length for each channel, but I just could not get channel 6 to come it. Channel 7 came it somewhat clear but with lots of interference. I adjusted my antenna per the guide, and the snow was very present. Any ideas what the problem is? Maybe this model just isn't strong enough even with the output level cranked. I just put it back on 16 for now.

What are you using for a recieve antenna for the tv set?

jr

For the initial set up, I used my 1976 Zenith CCII 13" table set with its built in dipoles.

I just got through rewatching Shango066's video about his antenna and I believe I will do exactly what he did and see if I can get the same results. The modulator works excellent on channel 16 UHF with just a simple loop - so good you'd think it was straight from the cable box. VHF, however, is much more elusive for me.

Have you tried another tv, or tested the low band VHF-reception of the zenith using ch 3 & 4 from a vcr?

jr

VHF lowband require large antennas. CH 2 is 54-60MHz of which the wavelength is just under 6 meters. The antenna must be a specific length based on the wavelength. Lowband antennas even for a quarter wavelength dipole are still large and unwieldy. Probably best to stick to UHF since the antennas are much smaller (on the order of 4-5 inches for a quarter wave or twice that for half wave. Plus UHF has the advantage of lower man made noise.

I've given up on VHF for a while. Just got too busy to try building a tuned antenna. Especially now that I have new Zenith to care for. Speaking of Zenith, I would like to find a Chromatenna to match my new Chromacolor. Anyone know where I can find one of those? Preferably NIB.

I have seen that antenna & others on E-bay, just have
to wait.....

Trouble on VHF may be interference. You have to flip all the breakers
but the one you need & see if it goes away. If not start unplugging
things on that line. Damn near everything that plugs in now
can cause it including pig tail light bulbs. My house had all
pigtails & I got rid of them except in closets. Had to to use
an AM radio. Past few yrs I am putting in rugged use 130V
real light bulbs since you can still get all wattages.

73 Zeno:smoke: