[TowerTalk] Strange Balun...please help

[Herbert Schoenbohm]

Yes indeed 800 ohms is perfect as a termination. This device seems to be 
a real brute and may have come from military surplus as they used T2FD 
antennas for many installations because their work was very frequency 
agile from 2-30 Mhz.  I guess since they had big QRO transmitters the 
induced termination loses were not a problem for them.  The T2FD is said 
also to be a fairly quiet antenna.


On 1/25/2017 12:45 PM, Perry Ogletree K4PWO wrote:
> It may be intended for a terminated antenna design like a T2FD or terminated
> sloping wire.  In those designs, you have a folded dipole with a termination
> resistor joining the ends for the T2FD or an end fed wire with a termination
> resistor at the far end to ground.
> The ratio may be 16:1 as they are usually multiples of 2 for a 800 ohm
> termination.  Check that with an antenna analyzer and see if it measures the
> same as the 1K ohm did.
>
> Perry K4PWO
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
> Herbert Schoenbohm
> Sent: Wednesday, January 25, 2017 9:26 AM
> To: towertalk at contesting.com
> Subject: [TowerTalk] Strange Balun...please help
>
> I came into the possession of two unusual high power baluns, one with 125'
> of RG-213 attached and the other with a two foot lead of coax attached.
> They are seal and inside PVC with the coax going inside the bottom and large
> eyelets for the wire and support in the center. They appear to be
> commercially made.  I soon found tat they are not current baluns judging
> from the discovery that there is no DC continuity to either wire connection
> from the coax.  With a bridge and a 50 ohm non-inductive resistor the VSWR
> is very high.  However when I put a 1000 ohm resistor on the antenna
> connections the balun is flat from 1.8 to past 60 Mhz.  This would make the
> device a 20:1 balun which is something I have never heard of. What kind of
> antenna requires such a high impedance feed?  If anyone has any knowledge of
> the use for these devices please let me know. Thanks
>
>
> Herb, KV4FZ
>
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