RAN Technology


 Posted By: Robert Nickels (ranickels)
Posted: 04/13/2021

Vintage Ham Radio 04/13/2021 

My SWR Dilemma

Learning about trap dipoles and SWR


 

When I got my Novice license in the fall of 1965, my dad had also decided that as long as he was taking me to the classes at Blue Valley Amateur Radio Club in Seward, Nebraska, he might as well try for his license too.    I was fortunate that not only were my parents supportive of my ham radio interest, but my dad could build anything.   So the first thing was a 40 ft. mast to support an antenna, which turned out to be a HyGain 2BDQ trap dipole.

 

 

Like most new hams, we didn't know anything about antennas or how easy they were to make, and the lure of two-band antenna from a company like HyGain in nearby Lincoln NE was strong.   I suspect we showed it to the guys at the club who said "Yeah, that outta work" and that was it.   The antenna worked like a champ for SWLing and following the instructions in my HT-40 manual I loaded it up and made contacts on both 80 and 40 meters.

For Christmas I received a Heathkit HM-11 Reflected Power and SWR Meter that by then had transitioned to the Heathkit Green color scheme like the one below.     I borrowed a muffin tin from my mom and carefully assembled it over the course of a day or two and eagerly connected it to my station.    Keying the rig I adjusted the Forward power for full-scale and flipped the switch to Reflected, expecting to see a nice flat 1:1 SWR but to my dismay is read 4:1.

How could this be?   I was able to make contacts OK and you coudln't do that with a horrible SWR could you?    Thus I assumed I must have messed up the SWR bridge assembly somehow and decided I'd just leave it in the Forward position so as not to be reminded of my failure.

A bit later, a ham who worked for the state repairing traffic signal lights was in town and paid a visit.  While giving him my station tour I explained my SWR bridge problem and he offered to get one out of his car and compare.   Guess what?  It read 4:1 also!

He offered to come back and tune my antenna to improve the SWR which I figured would make my signal really get out!  Hy Gain trap dipoles were made using some kind of stiff wire and clamps so it wasn't the easiest to adjust and after numerous attempts the fellow asked how strongly attached I was to the traps.  I said I just wanted something that worked, and he asked if I had any wire lying around.   Which we did - the traps came off and an  80-40 meter fan dipole took it's place, installed as an inverted-vee with each leg tied to a separate support.   The new diople tuned right to resonance like it should on his SWR meter AND on my Heathkit!

Even though it's since become fashionable to BUY antennas,  to me that lesson taught me that the best antenna  you'll probably ever have can be made with wire from the hardware store and a few insulators.

Some time later I guess I decided to give the old HM-11 a facelift to better match the color scheme of gray radios, but I still have it!

 

Click on the image title or on the image itself to open the full-sized image in a separate window.
   

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