DID I Blow up My RF Ammeters?

[KD6VXI]

So whats best?   There seems to be a line deviding people on this..


Throw up long wires, Run open wire down, Make your own tuner that will tune ANYthing. 

Cut the flat top and feeder so it is in the octaves of the ham band with the goal of not going on 1200 ohms on any band.


People really seem to be devided on this..  I have  a KW matchbox so I cant adjust the coil.  I require an antenna that works with this tuner.. that means 1200 ohms or less.  Others just keep modifying the tuner so what ever antenna they have, Tunes.  If you do this, Are you inducing loss?

C

Clark and others,
I'm thinking that the ops of the past were just happy to get a signal out. THey did not have the sophisticated gadgets we have now to see the shortcommings of improper lengths of feedlines or antenna lines and the impedances and reactance, etc.
Throw it up and tune it up.
Today we're going for the most we can get to be channel masters....yeah!!!

Fred

Fred,

I coined a term on an amplifiers mailing list once, dealing with this:

"MFJ, making engineers out of idiots"

What with the 259 and it's variants, actually learning the math behind the theory is a thing of the past!

--Shane (tongue in cheek)

[W1AEX]

So I advise trying to get the feed 1/8, 3/8, 5/8...wavelength.   In my case 92 feet was longer than I needed so I had to loop it out over the back yard in a wider loop to get it to fit.

Interesting Rob. I ran into issues with my 250 foot center-fed after building my new open-wire feedline, which I had cut to a convenient length of 90 feet. It tuned easily on all bands, except for the upper portion of 160 meters, where it got very nasty with lots of interesting arcing and spitting. I examined the "magic feedline formula" that you have indicated above, and found that all the touchy tuning issues ceased when I used an odd multiple of 1/8 wavelength for my feedline length. This meant using either 63 feet or 189 feet, plus or minus 10 feet or so. I did the looping feedline thing you described above for several months with excellent results, but it was physically awkward and brought jokes from my daughter-in-law about the long "hamster ladder" in the trees. So, I eventually used about 70 feet and it has been very happy with that length for 160-75-60 and 40 meters. I found that 80 feet to 100 feet induced the unhappy tuning issues on the top end of 160 meters. I have no background in antenna theory what-so-ever, but I would agree with you that the "lowest frequency to be used 1/8 wave-odd-multiple-magic-open-wire-feedline length" design does seem to work. Now, if I could just remember where I put my RF ammeters last fall, I could re-check the system for balance...

Rob W1AEX

[W2VW]

So whats best?   There seems to be a line deviding people on this..


Throw up long wires, Run open wire down, Make your own tuner that will tune ANYthing. 

Cut the flat top and feeder so it is in the octaves of the ham band with the goal of not going on 1200 ohms on any band.


People really seem to be devided on this..  I have  a KW matchbox so I cant adjust the coil.  I require an antenna that works with this tuner.. that means 1200 ohms or less.  Others just keep modifying the tuner so what ever antenna they have, Tunes.  If you do this, Are you inducing loss?

C

Clark and others,
I'm thinking that the ops of the past were just happy to get a signal out. THey did not have the sophisticated gadgets we have now to see the shortcommings of improper lengths of feedlines or antenna lines and the impedances and reactance, etc.
Throw it up and tune it up.
Today we're going for the most we can get to be channel masters....yeah!!!

Fred

The ops of yesterday looked for rated final plate current and probably a certain depth to the dip. That along with lack of heated parts would indicate max power transfer pretty close to what todays dips use. 

[Jim, W5JO]

The ops of yesterday looked for rated final plate current and probably a certain depth to the dip. That along with lack of heated parts would indicate max power transfer pretty close to what todays dips use. 

Being one, I used a florescent tube hung under the wire of my flat top.  I also used the two neon bulbs across the feedline. 

[K5UJ]

So I advise trying to get the feed 1/8, 3/8, 5/8...wavelength.   In my case 92 feet was longer than I needed so I had to loop it out over the back yard in a wider loop to get it to fit.

I have no background in antenna theory what-so-ever, but I would agree with you that the "lowest frequency to be used 1/8 wave-odd-multiple-magic-open-wire-feedline length" design does seem to work. Now, if I could just remember where I put my RF ammeters last fall, I could re-check the system for balance...

Rob W1AEX

Rob Thanks, but here's something I completely forgot, just to show you I am no antenna brainiac either:  I never thought to take into account the 95% velocity factor of ladder line in working out my 3/8 wave feedline length.   I wrote that 3/8 comes out to around 97 feet and I shorted it by fudging it, but when I figure in the VF it works out to being 92 feet and change.  I'd like to say I had it all figured out and nailed it but it was nothing other than dumb luck.

Rob

[ke7trp]

Ok.. Ok...  This weekend, I will add 10ft of line to the feeder, Restring it and rehang it.  I will report back.. 


I agree about the days past.. Hook it up and tune it.. The Champ and the king could careless and will match the line.. Heck, 20meters does work. But when I see that SWR meter showing 2.5 to 1 on 1, I just cant except that.. LOL


Clark