The AM Forum

I couldn't pass this up, although having a 299 khz 40 watt transmitter that weighs about 400 lbs is kinda weird!

This thing has a pair of 807s, modulated by a pair of 807s and a whole lot of Peerless transformers.

It's a type TMO beacon (NDB) transmitter built on a 1942 contract for the CAA.

(http://img11.imageshack.us/img11/5752/img8176r.th.jpg) (http://img11.imageshack.us/my.php?image=img8176r.jpg)

Lots of black wrinkle paint, four units on full extension slides, the units plug into the strips on the back of the rack when they're pushed into place and fan cooled. The bottom unit is the HV power supply with a pair of 3B28s and only running 600 volts. The next one up is the modulator with more Peerless transformers and a pair of PP 807s for modulators along with it's power supply. Next a two tube exciter running a huge 299 khz crystal feeding a pair of 807s. And on top a tuning coil with a nice relay and variometer. The four foot rack is welded into one piece and has 1/4 inch steel in the top and bottom units and weighs about 100 lbs. It's got nice meters and most of the controls are under the heavy duty doors on the front of each rack which also doubles as air outlets for the cooling air pulled into the rack by the fan in the lower unit through a filter. At some time in the past the fan seized up and some idiot just took off the back panel and let it cool by normal air flow. It's over built to the extreme (made to run 24/7 for years) and only has about 40 watts input to the final pair of 807s.

Tuning unit...

(http://img269.imageshack.us/img269/9333/img8170v.th.jpg) (http://img269.imageshack.us/my.php?image=img8170v.jpg)

Exciter and power amp...

(http://img20.imageshack.us/img20/6979/img8169e.th.jpg) (http://img20.imageshack.us/my.php?image=img8169e.jpg)

Modulator...

(http://img200.imageshack.us/img200/5484/img8161p.th.jpg) (http://img200.imageshack.us/my.php?image=img8161p.jpg)

Power supply and fan...

(http://img20.imageshack.us/img20/9325/img8164k.th.jpg) (http://img20.imageshack.us/my.php?image=img8164k.jpg)

Rack with units...

(http://img200.imageshack.us/img200/3552/img8159p.th.jpg) (http://img200.imageshack.us/my.php?image=img8159p.jpg)

I can't think of a good use for it as is, other than as a low power 160 meter station, but I think I'll try and figure if the transformers and case are large enough to build a legal limit AM rig out of. It is a good looking unit. I'll have to stop by again in Kansas City to pick up the rack since I couldn't get it all in the car in one trip. I forgot to take a picture before I pulled the units apart.

Does anybody have any info on this unit? I can't find anything on the web. I'll try the local FAA Airways maintenance shop but I suspect this has been out of service for awhile.

make a hell of a lowfer beacon transmitter. Did the powers that be ever grant ham privileges down in that area of the spectrum ?

Our current ham bands:
http://amfone.net/Amforum/index.php?topic=20050.0

There is some part 15 activity there and there are some licensed experimental stations there too.

I cleaned things up today and got the transformer numbers. It'd be cool to restore if there was a use but it's best use may be as a start of a buzzardly 80 meter AM rig. The main plate transformer is rated 1,200 vct @ 400 VA but if it was run as a full wave bridge you could probably pull near legal limit in amateur service. This thing was built to run 24/7 for years; the iron is pretty hefty.

http://www.500kc.com/ (http://www.500kc.com/)

proll wouldnt take much to get that puppy on 500. I hd a lo of fun with a WW2 navy longwave rx that tuned own to abt 15kc , yes, I mean kc and up to abt 500 on the high end. i let it go and then 6 years later saw it for sale at Gaithersburg hamfest. I had written some logging info on the chart on the front and knew my own handwriting right away of course.

almost bought it back.  ::)

Jay, W1VD (who posts here often on his receiver measurements) runs WE2XGR/2 on 505 - 515. I copied his beacon a few weeks ago with no problem, despite the summertime static.

how about some cleaned up pix to make me so horny?  ;D

Always happy to help!  ;D

This is after a quick clean-up on three of them, and as you can see, I haven't rounded up help to get the power supply out of the trunk, so about all I did there was clean the transformer tops so I could read the tags. The power supply fan sucks air through a 12 x 12 filter in the front panel and pressurizes the whole rack; the air outlets are screened and through the perforated covers on the fronts of the other units.

The thumbnails will enlarge when you click on them and enlarge again if you click on those...

(http://img194.imageshack.us/img194/2976/img8202s.th.jpg) (http://img194.imageshack.us/my.php?image=img8202s.jpg)

(http://img10.imageshack.us/img10/9932/img8207e.th.jpg) (http://img10.imageshack.us/my.php?image=img8207e.jpg)

(http://img10.imageshack.us/img10/3082/img8212q.th.jpg) (http://img10.imageshack.us/my.php?image=img8212q.jpg)

(http://img10.imageshack.us/img10/5808/img8229k.th.jpg) (http://img10.imageshack.us/my.php?image=img8229k.jpg)

(http://img188.imageshack.us/img188/9088/img8224s.th.jpg) (http://img188.imageshack.us/my.php?image=img8224s.jpg)

(http://img188.imageshack.us/img188/611/img8236n.th.jpg) (http://img188.imageshack.us/my.php?image=img8236n.jpg)

(http://img188.imageshack.us/img188/1834/img8237p.th.jpg) (http://img188.imageshack.us/my.php?image=img8237p.jpg)

(http://img188.imageshack.us/img188/8434/img8238m.th.jpg) (http://img188.imageshack.us/my.php?image=img8238m.jpg)

(http://img188.imageshack.us/img188/7017/img8244t.th.jpg) (http://img188.imageshack.us/my.php?image=img8244t.jpg)

(http://img188.imageshack.us/img188/7348/img8248x.th.jpg) (http://img188.imageshack.us/my.php?image=img8248x.jpg)

(http://img26.imageshack.us/img26/4697/img8252d.th.jpg) (http://img26.imageshack.us/my.php?image=img8252d.jpg)

(http://img26.imageshack.us/img26/6076/img8254n.th.jpg) (http://img26.imageshack.us/my.php?image=img8254n.jpg)

(http://img26.imageshack.us/img26/6885/img8256d.th.jpg) (http://img26.imageshack.us/my.php?image=img8256d.jpg)

I do have the nice big green lens for that light on the front of the power supply!  ;D

I'll throw in a gratuitous picture from the 4th of July!

(http://img224.imageshack.us/img224/6725/ddb20080704010222printwa7.th.jpg) (http://img224.imageshack.us/my.php?image=ddb20080704010222printwa7.jpg)

TY....that gives me wood. but then I think......all that for 4 807's??????? hmmmm...sub 814's or 828's.....tall and skinny....

on 299 now...that thing would so go up to 500. whutta lowfer transmitter. Personally I dont think I could cut that up.

I too, could get a antenna efficiency rating of .00000000000007%.....whoooo hoo.  :-\

that thing is mega cool, no doubt....

I'm gonna think long and hard before I change anything.

Judging by the tuning chart this thing ran with about 40 watts input to the 807s, but it was made to do it 24/7 for years at a time. I could change to outputs to something else and use a bridge on the plate transformer. It's rated at 400 watts continuous @ 600 volts and 670 ma. Full wave bridge would give me about 1,200 volts with a choke input filter (the secondary is 3,000 volt test) and I should be able to pull about 500 ma for 600 watts intermittent; I'd have to be careful of really long transmissions.  ;D

There are no power ratings on the modulation transformer, just impedance values.

Does anybody have a good Peerless listing? These transformers use numbers that don't match what I can find in catalogs. They have very low serial numbers (some matching), so I'm thinking that they were made for this contract instead of being stock transformers.

It'd make a great transmitter, but I'd hate to really modify it. If I do, I'll figure a way to do it with the minimum of butchery.

It'll be at least a year before I catch up on other projects and get the shack, with the BC-610, on the air. This one is way down the list.