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Author Topic: Antenna tuner for a portable G5RV  (Read 494 times)
KE7EOZ
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Posts: 117




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« on: July 14, 2007, 07:31:45 PM »

I am thinking to buy a antenna tuner to be use witha icom 706mkgii and a G5rv in portable situation, I would like to hera some feedback in between LGD Z-11 Pro or MFJ-929
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KE3WD
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Posts: 5694




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« Reply #1 on: July 14, 2007, 09:02:24 PM »

Let me try to get in here before Alan pops up with ye olde "this is a compromise antenna" spiel on ya.  (grin)

Either tuner should be able to tune the standard G5RV, certainly between 40 and 10, 80 too, although I consider 80 to be the "amplifier band" (grin).  

The MFJ touts a greater resistance tuning range in its specs but I doubt whether that will be a problem for you, if it is, try a longer feedline.  

On the other hand, the LDG will likely have the better rep from more hams.  

I don't think you could go too far wrong either way, personally, although I still prefer a good manual matchbox myself.  A big one with plenty of continuously variable L on each side.  Less to go wrong in the long run is the reason, though.  That and I'm likely to be carrying the amp along anyway.  

Nothing wrong with an auto matchbox, I've got a couple that I use, one mobile and the other built into one of the rigs.  I just like turnin' knobs I guess.  


This probably leaves you just where you were, IMO it may just be a coin flip.


.
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KE3WD
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« Reply #2 on: July 14, 2007, 09:06:52 PM »

BTW -- that LDG uses Latching Relays, which can be a significant advantage for battery portable ops.  

The MFJ doesn't mention latching relays at all, which means that it will have a higher current draw during operation.  

That would definitely bias me towards the LDG.  


.
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AD5X
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Posts: 1426




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« Reply #3 on: July 15, 2007, 05:08:55 AM »

For portable operation, I'm now using a MFJ-925 with my IC-706MIKIG.  This is a more compact version of the MFJ-929 (which I also have) with one output, and no LCD.  It works great.  R&L Electronics sells them for $160.  I recommend a radio interface cable, and you can easily make your own from the info in the MFJ manual.  Basically, get a short RJ45 terminated CAT5 cable, cut off the RJ45 on one end, and put the IC-706MKIIG 4-pin Molex connector on that end (using the wiring info in the MFJ manual).  You can get that 4-pin Molex connector from Radio Shack or Mouser Electronics (and probably Digi-Key and Allied Electronics).  I have reviews of the MFJ-925 and MFJ-929 on my website at www.ad5x.com.

Phil - AD5X
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KE7EOZ
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Posts: 117




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« Reply #4 on: July 16, 2007, 07:52:30 PM »

Now onother uqestion is I have rerad that some of those tuner you need a balun, in order to work right is that true, and do I need a balun for a G5RV?
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KE3WD
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« Reply #5 on: July 17, 2007, 10:22:12 PM »

>>>do I need a balun for a G5RV? <<<<


You should construct a simple coax coil 1:1 balun at the connection point to keep RF from being reflected back down the outside of the coax.

The antenna's inventor:

"Louis Varney warned against the use of transformer-wound 1:1 baluns because many designs show considerable losses when the load reactance is significant. Indeed, Jerry Sevick, W2FMI, who has published the most material on transmission-line transformers, recommends that all reactance compensation occur on the load side of the balun.

In place of such baluns to suppress common-mode currents, Varney recommends a 6" diameter coil of about 8 to 10 turns of the feedline coaxial cable at the junction of the matching section and the main feedline. "


I have used that ~6" dia. coil with success. Wireties, or electrical tape to hold it in form and in place.  Nice and neat, not scatter wrapped.  

Beware of those around the web claiming that you should not use the choke balun, hams can be fooled by better performance locally by that radiating coax.


Check out this article:


http://www.cebik.com/wire/g5rv2.html
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