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  #16  
Old 03-19-2016, 02:06 PM
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wa2ise wa2ise is offline
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Quote:
Originally Posted by Ed in Tx View Post
...

If you have a General or better amateur radio operators license (I have an Extra Class) you can indeed operate that transmitter if modified to operate at 1.8 to 2 mHz, the 160 Meter ham band. ...
Usually, having a decent antenna for 160 is harder. Especially for a kilowatt transmitter that expects a quarter wave antenna (like a tall broadcast tower). Oh, it can be done, but takes some effort.
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  #17  
Old 03-19-2016, 02:22 PM
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Ed in Tx Ed in Tx is offline
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Quote:
Originally Posted by wa2ise View Post
Usually, having a decent antenna for 160 is harder. Especially for a kilowatt transmitter that expects a quarter wave antenna (like a tall broadcast tower). Oh, it can be done, but takes some effort.
Yep. I've played with 160 M by loading up my 80-40-20 vertical which is about 40 ft tall with a capacitance load on top. Using a big loading coil I made from some scrap city sewer pipe about 8 1/2" diameter with about 20 or so turns of aluminum ground wire and alligator clip attachments to find a match with my MFJ antenna analyzer before I put power to it. No more than 100 W applied to it by me though.

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  #18  
Old 03-19-2016, 02:42 PM
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Quote:
Originally Posted by Charlie View Post
I'm kinda intrigued about the idea, but I need an AM radio station like I need a hole in my head!
That sort of thing can be said for almost all of us here, one exception being Jeff. A quote from The Simpsons' Apu comes to mind: "Must you dump on everything we do?"

Anyway, that's a fine catch. And I thought my old desk was heavy at about 300 pounds.

Last edited by Jon A.; 03-19-2016 at 06:38 PM.
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  #19  
Old 03-19-2016, 03:23 PM
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Quote:
Originally Posted by Ed in Tx View Post
Yep. I've played with 160 M by loading up my 80-40-20 vertical which is about 40 ft tall with a capacitance load on top. Using a big loading coil I made from some scrap city sewer pipe about 8 1/2" diameter with about 20 or so turns of aluminum ground wire and alligator clip attachments to find a match with my MFJ antenna analyzer before I put power to it. No more than 100 W applied to it by me though.
Some impoverished peanut whistle AM station owners, mostly in small towns have had a moderate degree of success with short heavily top loaded arrays such as this:

http://www.star-h.com/docs/STAR-H%20...esentation.pdf

jr
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  #20  
Old 03-19-2016, 05:43 PM
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Does your unit have the original (and scarce) 4-500 tubes in it, or did it get converted to the 4-400s?
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  #21  
Old 03-19-2016, 06:34 PM
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Just looked... I could make out 4-400C on one tube, so I assume they are all the same. I did happen to notice online that 4-500's were about 500 bucks a pop. Looks like the 400's run about 300... at least the new ones I saw.
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  #22  
Old 03-19-2016, 07:29 PM
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Used 4-400s and various substitutes are plentiful, as well.....4-500s not so much.
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  #23  
Old 03-30-2016, 09:06 PM
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As others have warned, attempting to put this thing on the air for its original purpose (running an AM broadcast station) would bring you serious legal trouble. Only way to use it as-is would be to acquire a licensed broadcast station. FCC only accepts new construction permit applications during an "application window". They haven't had a window for AM Broadcast since 2004 and are not likely planning another one.

Last I knew, licensed radio amateurs could modify equipment intended for other services if they can do it while meeting strict spurious emission requirements (Part 97 may be the only service where this is still true). If you were to modify it for the 160m band (1800-2000 kHz) by reducing the inductance in the coils, you could run the full kilowatt in CW (Morse code), but you would have to lower the power to about 375 watts when running AM phone (since this will produce 1500 watts at peak modulation).

80m (3500-4000 kHz) has much more activity than 160, and propagates further out at night, but your transmitter would need more drastic surgery - new tuning circuits in every stage.

One possibility is that you could sell it to a licensed ham who wants to put it on the air. (Check current regs first, it's been awhile since I was on the bands).

Last edited by Robert Grant; 03-30-2016 at 09:27 PM.
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  #24  
Old 04-14-2016, 08:07 AM
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It probably has a power cutback to either 250 or 500W...possibly both. I've worked on one of those McMartins a long time ago...not a bad rig. 160 conversion is EZ...80 not quite so but doable.
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  #25  
Old 04-25-2016, 09:50 PM
3Guncolor 3Guncolor is offline
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It might be fun to run it into dummy load. Looks like it's all there don't part it out tube rigs are getting rare. If it has power cutback it will reduce the power consumption, unwanted RF radiation and increase the tube life.
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  #26  
Old 05-14-2016, 01:20 PM
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Quote:
Originally Posted by 3Guncolor View Post
It might be fun to run it into dummy load. Looks like it's all there don't part it out tube rigs are getting rare. If it has power cutback it will reduce the power consumption, unwanted RF radiation and increase the tube life.
I'm betting there may well be a built-in dummy load...lots of 1kW AM rigs had them...usually a bunch of big resistors mounted up near the top of the cabinet & possibly some sort of switch/jumper arrangement to switch from antenna output to the dummy. Can't recall if the McMartin I worked on 30-odd years ago was so equipped.
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  #27  
Old 05-24-2016, 09:27 PM
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Late to the party, but for potential buyers, how about state/local agencies, for traffic information stations? IIRC, there are two fixed frequencies in each operation area for such public service broadcasts - perhaps a locale with only one frequency used, and would like to add a second? Overkill, perhaps, but just a thought.

Or, Charlie, take it to sea and be a Pirate radio operator. 12 Miles out, say??
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  #28  
Old 03-17-2019, 11:34 AM
Tim Tress Tim Tress is offline
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Many hams are converting old tube AM broadcast transmitters for AM use on the 80 meter band. A Google search will bring up some information.
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  #29  
Old 03-17-2019, 07:00 PM
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I never operated 160m when I had my OTA ham station in suburban Cleveland. The vertical and dipole antennas I used were not tunable to 160. Never used any kind of high power transmitter, either; the highest power I ever used was 100 watts, from my Icom IC-725. 160m does not apply to my current setup (Echolink), since it is not OTA ham radio but purely streaming audio over the Internet, with the capability to link to other stations and even control other stations remotely. I also operated 2 meters through local FM repeaters.

However, I did play with a 0.1-watt (100mW) AM transmitter (Lafayette Radio KT-195, three tubes, 2 50BM8s and a 36AM3 rectifier tube) in the early 1970s, putting a very small (!) AM radio station on the air for about a year and a half from my home town. I couldn't use any kind of outdoor antenna with it, so was restricted to the wire antenna which had been supplied with the kit; any kind of longer antenna would have caused the transmitter to put out some level of power over 100 mW. The transmitter put out a strong enough signal (!) with its supplied antenna, however, to be heard only about five hundred feet either side of my home; the best reception report I ever had with this super-peanut whistle was in the spring of 1971, when someone reported hearing the signal at the corner of my street, near the mailbox. Conditions must have been extremely good that day as I never received another reception report like that again, from then until the station signed off for the last time.

I had to give up the station when I moved in 1972 (long story), but it was a lot of fun while it lasted. My amateur radio station, WN8NHV, however, replaced it (I had received my Novice ticket shortly before I moved; got the station on the air 97 days later).....and the rest is history.

BTW, I would think using a 1-kW broadcast transmitter on 160 meters would be illegal, to say nothing of the fact that hardly anyone uses AM on any amateur band (except perhaps six meters) anymore. These transmitters were not intended to be used on the amateur bands; moreover, the modifications required to allow the transmitter to operate on 160 meters (or any other amateur band) would probably, even likely, void the transmitter's FCC approval, which would be valid only as long as the transmitter was operated within the AM broadcast band. I remember seeing a cartoon in one of the electronics magazines (Electronics Illustrated, long since defunct, comes to mind) in which an amateur was in a jail cell, talking to his cell mate. The amateur had been cited by the FCC for calling CQ on the AM broadcast band, over a 50-kW broadcast transmitter. I'll never know, but my best guess is the man lost his amateur license as well as having had to serve the prison sentence. There was also the story of a woman who was an announcer, on the night shift, at a traffic-information station on 530 kHz. The station was legal, but the woman got bored after several nights of announcing only traffic reports; she eventually started singing and playing records over the station, and was eventually fired for illegally playing music over a TIS radio station. The company or concern to which the station was licensed probably was cited as well.
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Last edited by Jeffhs; 03-17-2019 at 07:43 PM.
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  #30  
Old 03-18-2019, 07:03 PM
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Well, it hasn't moved anywhere. It still sits in the same place it did when I got it home a couple of years ago. It really needs to find a new home.
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