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   Home   Help Search  
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 51 
 on: Today at 07:05:58 AM 
Started by DU7DVE - Last post by AC2EU
 I was wondering:
If the antenna "tunes 1:1 on most frequencies" , why are you messing with it?
No antenna will be perfect on all frequencies.

The antenna is a 'system" which is a mix of all of its components, including the feed line, height, proximity to other objects, etc.
If you changed the length of the feed line, there would be a notable change in the way the antenna tunes on various bands.
I sounds like you already have a pretty good balance of the components, so you might as well
leave it the way it is.
Otherwise get an antenna analyzer and see what impedance is being presented at the end of the  feed line. ( use a binding post adaptor and calibrate to it) Then you will know what is going on for sure.

 52 
 on: Today at 06:09:36 AM 
Started by WB8PFZ - Last post by WB8PFZ
Someone just listed some on Ebay. In my opinion the easiest way to buy parts.

 53 
 on: Today at 06:03:57 AM 
Started by WA3RSL - Last post by WA3RSL
Thanks Val. I won't touch my Acom 1000.

73

Frank
WA3RSL

 54 
 on: Today at 05:24:35 AM 
Started by DU7DVE - Last post by KD7RDZI2
are you sure the 4:1 external transformer are baluns? Many confuse baluns with ununs. The one in the MFJ tuner I believe is a balun, so maybe the external ones might be simply ununs. Adding a choke (which is the same of the so called Line Isolators or 1:1 guanella baluns) between the tuner and close to the external transformer might allow you to get a better match. As others have said you might not even need a 4:1 transformer (either balun or unun). Do not be surprised in the case you get a worse SWR adding a 1:1 balun. It can happen. Look at the 1:1 balun as a sort of RF isolator, adding it close to the antenna will RF isolate the cable from the antenna and this can change the SWR. In some cases the SWR gets worse simply because the coax is not part of the radiating system anymore. Doing this means the noise you receive comes from the antenna only and not from the outer of the coax. By the way a MFJ-915 is a fine and reasonably priced 1:1 balun you can always add at in your antenna system.

 55 
 on: Today at 05:07:25 AM 
Started by AK0B - Last post by W5DXP
...They (transmission line currents) also do not canceL ... the radiation from the antenna-mode currents...

Adding the highlighted context resolved the ambiguity. Thanks.

 56 
 on: Today at 05:01:36 AM 
Started by N3DT - Last post by K8AC
Check out the meter face software available for free.  Here's one I've played with:

http://www.tonnesoftware.com/meter.html

If you print a meter face on photo paper, it will be pretty crisp and look about as good as a commercial scale.  The new face could just be glued to the existing meter scale -most can be easily removed for this work.

73, Floyd - K8AC

 57 
 on: Today at 05:00:07 AM 
Started by WH6WJ - Last post by KF4ZGZ
Here's an idea I have for temporary antennas.
Use a grappling hook made from kinda strong wire. But not to strong.
Thick copper, coat hanger, etc.
If you don't get it where you want, a good pull will straighten out the hooks and let it drop.
Re-bend the hooks, sling, throw, shoot it again.

I plan on using copper to hold an endfed when on vacation .... then pull it and go.


Matt

 58 
 on: Today at 04:14:18 AM 
Started by AK0B - Last post by G8HQP
Quote from: W5DXP
Seems they either cancel radiation and therefore don't radiate or they "do not cancel radiation" and therefore radiate. See why I am confused?
No, I don't see why you are confused. The transmission line currents do not themselves radiate as they cancel each other due to being equal but opposite in direction yet close together. They also do not cancel (or enhance) the radiation from the antenna-mode currents, which are equal and in the same direction. In addition, the transmission line currents are usually much smaller than the antenna-mode currents. So they do not radiate, and they do not cancel (or enhance) radiation; they simply cancel each other.

There is a tiny exception: the transmission-line currents in the shorts at the ends. These will radiate, but as the line spacing is usually small there will be little radiation so this effect can usually be ignored.

 59 
 on: Today at 03:17:47 AM 
Started by KF7DS - Last post by W9IQ
Spelling error on my last post - it should read choking balun.

- Glenn W9IQ

 60 
 on: Today at 03:12:46 AM 
Started by W6EM - Last post by W9FIB
Go back and look at some of the Hamvention photos of mud everywhere in the flea market.  JX may not have been there, but his commentary matches that of others that attended.

It does? Manure filled buildings? Traffic problems beyond Friday? Cattlefest? And many other examples that don't concur with what many people have said in their descriptions that they themselves witnessed.

What's even funnier is even proven wrong the same story keeps coming from the JX world. And 29000 + people all are liars cause only JX is right? Oh wait, in another thread DARA padded the attendance number. Only the JX world can make this stuff up.

The JX world just can't accept the truth of thousands over his own mindset.

Are you breathing the same fumes JX does?

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