[HCARC] Antenna Coupler vs Antenna Tuner (Gary J's weekly test tosee if the Reflector is still working)

[Gary and Arlene Johnson]

Thanks Kerry, but is it better to have the tuning/coupling done in the shack 
or at the antenna.  What you quoted from the Handbook sort of said best at 
the antenna and then gave examples in the shack.  Go figure that out.  I was 
reading an article where the author said that having the antenna coupler at 
the antenna didn't waste all the enegy heating up the coax between the 
antenna and the shack.  Sounded ok to me so I thought I would ask my 
resident experts.  Within reason, anything I can do to not waste RF energy 
and DB's is a good thing.  RF is best going out the antenna as signal vs 
warming Kerr County.

BTW, I may have solved the Code Key problem.  The guy I got my tower from is 
sending me a Brown Brothers CTL-B double key set in like new condition for 
less than J-38's are selling for on Ebay.  BTW, there are J-38's (restored 
ones) selling for upwards of $125.00 on Ebay.  Do you know of a place where 
one can buy parts for Ham Keys like J-38's??  Or is it a buy three to make 
two proposition??  My code study is coming along.  I probably know 12 to 15 
letters wihout thinking about them so far.

http://www.ebay.com/itm/Vintage-Lionel-J-38-Telegraph-Key-Signal-Corps-U-S-Army-/181031633565?pt=US_Code_Keyers_Keys&hash=item2a2653829d

Gary J
N5BAA
HCARC Secretary 2013


----- Original Message ----- 
From: "Kerry Sandstrom" <kerryk5ks at hughes.net>
To: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>; 
<hcarc at mailman.qth.net>
Sent: Saturday, December 22, 2012 3:26 PM
Subject: Re: [HCARC] Antenna Coupler vs Antenna Tuner (Gary J's weekly test 
tosee if the Reflector is still working)


> Hi Gary,
>
> There sure hasn't been much on the reflector lately.
>
> I'm not sure there is any difference between an antenna coupler and an 
> antenna tuner.  If you have a XCVR/XMTR that is designed for 50 Ohm 
> output, and if you are using a transmission line that has a different 
> impedance, then you need an impedance matching network between your XMTR 
> and the transmission line.  It could be an RF transformer or it could be 
> an antenna tuner/coupler, and it could be manual or automatic.  Many 
> antennas have matching networks.  A gamma match is a matching network: it 
> transforms the 50 ohm transmission line impedance to the impedance 
> required to drive the driven element.  Just because it looks like its part 
> of the antenna makes it no less of a matching network.  A lot of things in 
> radio have multiple names.  A good example is condenser and capacitor. 
> Condenser is the historical name and capacitor is the modern name.  Old 
> transmitter finals typically had two controls: "Final Tuning" and 
> "Loading".  Early transmitters often had two controls labeled "Final 
> Tuning" and "Coupling". The "Coupling" control was often a mechanical 
> adjustment that changed the inductive coupling between the primary and 
> secondary coils of an RF transformer.
>
> A quote from the ARRL Radio Amateurs Handbook, 25th Edition 1948.  "The 
> apparatus used to cancel line reactance and match the line resistance to 
> the transmitter is commonly called an "antenna coupler" or "antenna 
> tuner." (The name is really a misnomer, because the coupling and tuning 
> equipment at the input end of the line does not have any effect on the 
> antenna itself; if there is any antenna tuning to be done it must be doone 
> at the antenna, independently of the line.)"  The handbook goes on to show 
> several designs for "Antenna Couplers"s all intended to be in the radio 
> shack next to the transmitter.  Incidently, all are for parallel wire 
> transmission lines since this is from right after WWII and hams had not 
> yet started to use coax cables.  The 1968 handbook still had an article on 
> a "Wide-Range  Coupler for Balanced Transmission Lines."
>
> As you can see there is no difference between an antenna coupler and an 
> antenna tuner.
>
> There is nothing dangerous about an antenna switch.  There are two 
> problems with antenna switches.  First, most people use them for 
> convenience and don't disconnect their antennas from there equipment to 
> prevent lightning damage.  They rely on the switch to protect their 
> equipment.  DON"T!!  IT WON'T.  The second problem is all switches and 
> relays have leakage.  The formerly popular Dow-Key coax relays are good 
> for about 60 dB of isolation at HF.  At VHF and UHF, the isolation gets 
> very low.  In days past, hams have literally fried their low noise 
> receiver front ends (expensive tubes and transistors!) because of leakage 
> between the transmit side and receive side of coaxial relays.  Coax 
> switches have the same problems.  Typically a station will use a coax 
> switch to switch between a couple matched 50 Ohm antennas, a 50 Ohm dummy 
> load and an antenna tuner.  There is nothing inherently unsafe about this. 
> By the way, if you're looking for a coaxial T-R switch for a high 
> power/low noise station setup at UHF, expect to pay $1000 or so for that 
> relay.  They aren't cheap and they don't use PL-259/SO-239 UHF Connectors.
>
> Kerry
>
>
>
>
>
>
> -----
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