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 Post subject: Long wire antenna (beverage) matching transformer
PostPosted: Nov Wed 07, 2012 4:23 pm 
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Joined: Jul Sun 15, 2012 9:13 pm
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I am in the process of installing a Beverage antenna. I am terminating the far end with a 600 ohm resistor to ground. I'm going to require a fairly long down lead to get to the reciever.
If I use a 50 or 75 ohm coax to get to the reciever, where can I purchase a matching transformer or parts to make one? Also, is there another way to get to the reciever that does not require a transformer? Thanks TOM


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Wed 07, 2012 8:17 pm 
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Location: Palmerston North, New Zealand
Google for:

Impedance matching a beverage antenna to a receiver

by Nicholas Hall-Patch and John H. Bryant.

It's on this website - www.dxer.ca

It gets quite technical in the middle but the final product at the end is quite simple. I have a similar transformer for my (short 66ft) longwire to 50ohm coax back to the receiver which works well.

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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Wed 07, 2012 9:45 pm 
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Joined: Jan Mon 04, 2010 2:25 am
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Location: Finger Lakes of NY
Image

I have used a long wire antenna for several years with the wire going to various radios. I recently put an RG58 coax from the end of the wire to the radios. Somewhere (ARF?) I saw to use TV 75Ω to 300Ω adapters for radio use. I have pictured the ones I had lying around. I put an RG59 push on connector on the RG58 and just change it from radio to radio. Works very well. The biggest one on the right seems slightly better than the rest.

Hope this is some help,

Bill


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Thu 08, 2012 7:33 am 
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I'm not too sure that a TV balun will cover down to the 100kHz that you expect your beverage to work to.

The material of the core will be wrong and the turns on the primary and secondary also.

A good ole' FT50-43 with 35 turns on the primary and 11 turns on the secondary wound symmetrically works fine for me.

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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Thu 08, 2012 1:04 pm 
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Location: Leo, IN or Zellwood, FL
majoco wrote:
I'm not too sure that a TV balun will cover down to the 100kHz that you expect your beverage to work to.
The material of the core will be wrong and the turns on the primary and secondary also.
A good ole' FT50-43 with 35 turns on the primary and 11 turns on the secondary wound symmetrically works fine for me.


Agree with Marty that the TV baluns don't work correctly at MW frequencies. Also if your putting this antenna onto one of our OLD radios the radio is looking for high impedance around 600 ohms. So you need a second Transformer at this end of the coax to transform the 50/75 ohm coax back to 600 ohms for the old radio.
John k9uwa

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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Thu 08, 2012 7:58 pm 
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Joined: Jul Sun 15, 2012 9:13 pm
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I found a place to purchase the FT50-43 Ferrite toriod online but have some questions:

1) What type of wire should I use for the Primary and Secondary and is there directions online that show how to wind them?
2) What type of downlead wire should I use if using the FT50-43?
3) Should one end of the prim. and one end of the Sec. be grounded?
4) Does the downlead end at the the Reciever end require another matching transformer?

Thanks Tom


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Thu 08, 2012 8:38 pm 
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Winding instructions are contained at the end of the document that I sent you the URL. 35turns on the primary, 11 on the secondary with the secondary wound over the whole length of the primary. I have mounted my transformer on the ground rod and connected one end of the primary to it. The coax is connected to the secondary but not to ground - the ground connection is back at the receiver.

There are some other documents written by John Bryant on the construction of Beverage matching transformers and how to construct the 'best' one. Look here....http://www.dxing.info/equipment/.......and scroll down to "Impedance Transformers".

Given that the impedance at the end of a Beverage is quite variable, your downlead could be cheap TV 75ohm stuff, preferably with a double screen (the silver paper and the braid). You won't notice the difference in mismatch.

You haven't mentioned what receiver you will be attaching to the coax - if it has a coaxial connector then that is what you should use. Otherwise you could build another transformer to step up the impedance but to what - I don't know! Unless of course it's written on the back of the radio :D .

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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Thu 08, 2012 10:02 pm 
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Joined: Jul Sun 15, 2012 9:13 pm
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Thanks for the great info. I have many old radios (from the 20's to the 40's) that I have refurbished. Iwas going to try this antenna on various radio's. They all have screws in the back of the chasis to connect the antenna. I think I read above that I would probably have to do another transformer to get to around 600 ohms at the RX end for radio's of this age? I'll check the schematics to see if that info is available. Tom


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Fri 23, 2012 2:39 am 
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Joined: Jul Sun 15, 2012 9:13 pm
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I orderred the parts to make the matching transformer. I have a few questions about the hookup of this transformer:
Some diagrams online show the windings on the transformer going to the antenna wire with the other end going to a ground and the windings going to the receiver 75 ohm cable with one end going to the 75 ohm center conductor and the other going to the 75 ohm shield and to ground. To me this seems like a problem. If one end of the winding on the antenna side goes to ground, won't that ground out the signal? and if one end of the primary and one end of the secondary go to ground dosn't that electriacll connect the the two windings? Am I looking at this wrong? Thanks Tom


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Fri 23, 2012 3:05 am 
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I don't see much wrong with that. It's a transformer with a primary and a secondary - you feed the signal in at the top of the primary and connect the bottom of the primary to ground. Then the signal goes through the core to the secondary. You connect your coax braid to the bottom of the secondary and the signal comes out at the top to your coax centre wire.

Just like this...

Image

Now whether you connect the ground to the coax has always been a matter of opinion - my best answer is "suck it and see"!

You have three choices...
1. Connect the coax braid and the secondary bottom to the local ground.
2. Connect the bottom of the secondary to the local ground but don't connect the coax braid to anything - except the receiver of course.
3. Don't connect the secondary to anything except the coax.

My system works best with solution 3 - but it's not a Beverage - just a longish wire.

If you know anyone who has been suckered into buying one of those PAR SWL antennas, then the UN-UN box they supply has three terminals to allow the braid to be connected anywhere as above.

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Cheers - Marty ZL2MC


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Sun 25, 2012 10:46 pm 
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Joined: Jul Sun 15, 2012 9:13 pm
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Thanks. Now that I converted the beverage impedance to 75 ohms for my coax., I now need to build another impedance matching transformer to get to the impedance of my antique radio antena input. I found a calculater online that tells me the primary and secondary turns required after inputing the impedance's. I assumed a Rx antenna impedance of 600 ohms. So to get from 75 ohms to 600 ohms the calculator said to mulitply the primary turns times 2.828 to get the Secondary turns, so 2 turns on the prim would require about 6 turns on the Sec. Does this sound reasonable?


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Mon 26, 2012 3:27 am 
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Joined: Oct Sat 20, 2007 3:36 am
Posts: 14393
Location: Southern NH, 03076
I use the BN73-202 which has been the Beverage choice of most for at least a decade. In my case I have five two wire reversibles for 10 directions.
Wind only as a transformer and not as an autotransformer to minimize common mode pickup. Additional ferrite such as a large 31 Mix toroid wrapped with RG6 may be needed.

Formulas are here:

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=19733
http://www.maxmcarter.com/classecalcs/tratiocalc.html

Carl


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Mon 26, 2012 10:33 am 
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Quote:
So to get from 75 ohms to 600 ohms the calculator said to mulitply the primary turns times 2.828 to get the Secondary turns, so 2 turns on the prim would require about 6 turns on the Sec. Does this sound reasonable?


Radio is an exact science +/- 50%!

All you need to do is to make another transformer exactly as you made to go at the far end of the coax except wire it in reverse - low impedance to the coax and high impedance to the radio. Same number of turns to keep the reactance the same. Now you'll have 11 turns on the primary and 33 on the secondary - don't forget to ground the outer of the coax! The mismatch from using 75ohm coax or 50 or whatever won't matter diddley.

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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Tue 27, 2012 8:55 pm 
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Joined: Jul Sun 15, 2012 9:13 pm
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Thanks. Is an aluminum ground wire OK to use as a ground/earth wire? If not what gauge would be acceptable?


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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Nov Tue 27, 2012 9:33 pm 
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Location: Palmerston North, New Zealand
It depends on where the wire goes to! I use a bit of the same wire that I used for the antenna. I have an 8foot earth spike driven into the ground just below my mast and all grounds go to that. I leave the garden hose dripping on it for weeks on end in the summer to keep the conductivity up.

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 Post subject: Re: Long wire antenna (beverage) matching transformer
PostPosted: Dec Tue 04, 2012 12:18 am 
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Joined: Jul Sun 15, 2012 9:13 pm
Posts: 27
Thanks for the help from everyone. It was a nice day today so in completed my Beverage antenna with the proper down lead and matching transformers. It works great for my Antique radio's Am and SW with very little noise. Tom


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