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Have had the dream to put a SW on the air?

Posted: Sun Apr 13, 2008 4:19 pm
by w4cl
Having engineered AM, FM, analog TV and now digital TV, I have been thinking of what it would take to get a SW station on the air. Nothing like a VOA mind you, but if you had to get something on in a budget, exactly would COULD you get by with and what WOULD the FCC actually license. I know you have to have 50kW min to get licensed, but beyond that, it looks like the sky is the limit on what you use. I did find it interesting that WBCQ uses a modified 40 meter yagi beam for one of its systems and the FCC licensed it.

I have an idea of what I would try if I won the lottery since I don't see this thing making any money beyond the Pay and Pray crowd. Any takers on ideas?

Re: Have had the dream to put a SW on the air?

Posted: Sun Apr 13, 2008 6:20 pm
by K9EZ
w4cl wrote:Having engineered AM, FM, analog TV and now digital TV, I have been thinking of what it would take to get a SW station on the air. Nothing like a VOA mind you, but if you had to get something on in a budget, exactly would COULD you get by with and what WOULD the FCC actually license. I know you have to have 50kW min to get licensed, but beyond that, it looks like the sky is the limit on what you use. I did find it interesting that WBCQ uses a modified 40 meter yagi beam for one of its systems and the FCC licensed it.

I have an idea of what I would try if I won the lottery since I don't see this thing making any money beyond the Pay and Pray crowd. Any takers on ideas?

Wire antennas work just fine. You will need a good amount of land, but nothing like an AM array. There are a few SW station in North Carolina. Look up WBOH or WTJC in Newport, NC. It is a simple rhombic on telephone poles. I may have a pic or two around here of the WTJC system.

What else do you want to know?

Re: Have had the dream to put a SW on the air?

Posted: Sun Apr 13, 2008 10:31 pm
by Sam Buca
From my stomping grounds....the famous WMLK: http://www.wmlkradio.net

250kw xmtr :mrgreen:

Re: Have had the dream to put a SW on the air?

Posted: Mon Apr 14, 2008 5:49 am
by w4cl
If money were no object, instead of buying a old 50kW AM rig and converting it to SW, wonder what a sold state Nautel or similar would cost. Could the cost difference be made up in a reasonable time frame since you take out the cost of tube replacement and increase the reliablity quite a bit. Basically putting the cost on the front end, instead of the back end with tubes. Just a thought.

Re: Have had the dream to put a SW on the air?

Posted: Thu Aug 14, 2008 11:36 am
by K4WRF
If you buy a Nautel, you get a Continental SW rig. 15 years ago, they were about $600k per copy for a 100kW rig. A 5 w/l rombic with support poles comes in at about 25% the cost of TCI antenna and meets the beam width and gain requirements. If you have installed TV transmitter, you have a good idea as to the assembly of a SW transmitter. Tubes include PA and driver, PA is 4CW100,000 and driver is 4X3000, Tube life was very good, vac-caps seemed to fail a lot as they were excercized several times a day. Might want to try to attend HFCC to network and find frequencies that will work. Frequency coordination is key of course and FCC paperwork is minimal compared to US commercial requirements. I worked on the WWCR facility from when it started until about three years ago and I can tell you that was a money printing operation and it still is today. I will warn you SW broadcasting is another world from regular BCB, only some technical principals apply.
Good luck,

w/

Re: Have had the dream to put a SW on the air?

Posted: Thu Aug 14, 2008 11:47 am
by K9EZ
K4WRF wrote:If you buy a Nautel, you get a Continental SW rig. 15 years ago, they were about $600k per copy for a 100kW rig. A 5 w/l rombic with support poles comes in at about 25% the cost of TCI antenna and meets the beam width and gain requirements. If you have installed TV transmitter, you have a good idea as to the assembly of a SW transmitter. Tubes include PA and driver, PA is 4CW100,000 and driver is 4X3000, Tube life was very good, vac-caps seemed to fail a lot as they were excercized several times a day. Might want to try to attend HFCC to network and find frequencies that will work. Frequency coordination is key of course and FCC paperwork is minimal compared to US commercial requirements. I worked on the WWCR facility from when it started until about three years ago and I can tell you that was a money printing operation and it still is today. I will warn you SW broadcasting is another world from regular BCB, only some technical principals apply.
Good luck,

w/

You mean like these???
http://picasaweb.google.com/kwinrich/WYFR

Re: Have had the dream to put a SW on the air?

Posted: Thu Aug 14, 2008 12:40 pm
by K4WRF
Yeah, Continental uses a steam tube but over-flows the boiler making it water cooled. Boiler is also plate blocking cap. Water flows in through rubber hose and falls back down into a pirex duct that isolates the PA and returns distilled water to the tank, that is then cooled by running it through a fan cooled heat exchanger outside then back. Do these have tube modulators or have they been modified to solid state step modulators? I thought I saw a big transformer and choke in one of the pix. Thanks for the photos, very interesting indeed.

w/

Re: Have had the dream to put a SW on the air?

Posted: Thu Aug 14, 2008 12:47 pm
by K4WRF
BTW: I like that pix #20 showing air-cooled PA tube with the "swinging" plate by-pass choke.

HiHi...

73'

w/

Re: Have had the dream to put a SW on the air?

Posted: Sat Aug 16, 2008 3:27 pm
by w4cl
Don't they EVER clean those transmitters? Good thing my boss doesn't work there!! :twisted:

Re: Have had the dream to put a SW on the air?

Posted: Sun Nov 16, 2008 6:38 pm
by ai4i
Unless you really have something up your sleeves, not to mention pants with deep pockets, why not take this project on from a third world country?
You could operate from a Caribbean island with a few thousand watts or even a few hundred watts in one of the tropical bands (60m, 90m, or 120m), and cover everywhere from the north coast of Brazil to the southeastern United States.

Re: Have had the dream to put a SW on the air?

Posted: Mon Nov 17, 2008 2:34 pm
by RFWarrior
K4WRF wrote:If you buy a Nautel, you get a Continental SW rig.
In all fairness, that's not totally accurate :)

If you ask Nautel for a shortwave transmitter, we will refer you to Continental, but we don't sell them under any logo :) We looked at it, and we do build similar technology, but Continental is the gold standard in that field and there's just not enough market to pay the cost of development, not at the moment anyway. Too many other things on the go :D

Best,

Jeff

Re: Have had the dream to put a SW on the air?

Posted: Fri Jan 02, 2009 2:47 am
by LA_Guy
The easiest antenna I have seen to build is the vertically polarized corner reflector. For the 41 meter band, build an insulated 35 foot Rohn 25. You need a buried radial ground system under it, but the radials only need to be 35 feet long. Put up a screen made of 3 more towers (or phone poles) to make your corner reflector. Chain link fence soldered together would prpobably work for the rellecting material, or screen or even heavy duty chicken wire. The back of the corner reflector goes about 17 feet behind the radiating tower.
This is a nice, compact, cheap antenna that meets FCC gain requerements. Several SW stations in the USA use them successfully.

http://www.antennex.com/Sshack/pcr/pcr.html" onclick="window.open(this.href);return false;

http://yu1aw.ba-karlsruhe.de/shorten3dcra.pdf" onclick="window.open(this.href);return false;

http://books.google.com/books?id=OAJ1OA ... #PPA387,M1" onclick="window.open(this.href);return false;

Re: Have had the dream to put a SW on the air?

Posted: Fri Jan 02, 2009 4:58 am
by K9EZ
Huh had not seen those...but nice idea. Now to make one for the ham bands...... 8)

Also, welcome to the group. Hope you intro yourself in "Everything Else"