From: Vadim Kogan (vadim@XCF.Berkeley.EDU)
Date: Mon Mar 21 2005 - 09:31:04 PST
Well, now I have...
Yes, moving C8 "up" seems to get things to be rather nice. However, a better
report is to happen later, as I get to bring this whole setup to a HAM guy
with a proper antenna analyzer (besides, he'd have more clue when it comes
to making sure I'm not missing anything during the testing).
I have rather stupid SWR meter (in RCI 2950). It does not give an SWR
reading, but rather shows SWR as bars (less bars -> closer to 1). There
seems to be quite some range (for the C8 adjustment) where I get no bars.
Also the antenna seems to have a rather good bandwidth (I get no bars on 1,
19/20, and 40).
However, whether the setup is grounded to the vehicle or not does make a
difference. As you go up on that capacitor adjustment, you bring down the
SWR when the setup is grounded to the vehicle, but then you start increasing
the SWR for the "ungrounded" case. This is somewhat expected, but I was
hoping that for a vertical dipole it wouldn't be that critical.
I'd also like to mention that my testing is definitely bad, this was just a
bit of playing around to see the effects of C8 tuning. I was actually doing
this in the garage (with the antenna on the vehicle, but still indoors).
Obviously, the real tuning will be outdoors (and with a real analyzer).
I'd also like to figure out what are the parameters of that capacitor. The
only thing I can read off it is:
SGE (3|8)739 PC(5|S) 0H230
(x|y) means that it's either 'x' or 'y' (I couldn't read it too well).
I put a meter on it, but it didn't give me a usable reading :-( If anybody
could tell me what kind of capacitor it is, I'd really appreciate it. I have
a gutted base (everything was rusted) and it seems if I have a similar
capacitor, it's all I need to make that base usable for CB.
Vadim.
On Fri, Mar 18, 2005 at 06:57:33AM -0500, Stu Ellis wrote:
> Hi Jim!
> Has anyone tried it??
>
> From: "prcradio" <km6ab@p...>
> Date: Wed Aug 27, 2003 3:31 pm
> Subject: Re: Modify an MX-6707 with AS-1729 for use on CB?
>
> Here are some instructions I gave someone a while back, don't know if
> they did it or how it worked but it's worth a try:
>
> Take the bottom cover off the 1729 and look at the bottom of the ant
> with the coax cable/connector facing you. Find the 5th tuning
> capacitor
> (small screw driver adjustment) counting from the coax cable in a
> counter-clockwise direction. This capacitor (C8) tunes the lowest band
> 30-33mhz on the antenna and will probably allow you to match the
> antenna at 27mhz. You will need to have the whip attached and
> preferably mount the antenna on the vehicle. If not mounted, tune the
> antenna on a wooden ladder, away from any large metal objects. This
> antenna does not require a ground plane.
> Hope this helps.--
>
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