-=> On 09-27-97  06:13, Jeff Edmonson said to Ivy Iverson,<=-
-=>"About High Gain Antennas for 2M...,"<=-
-=> On 09-25-97  10:30, Jeff Edmonson said to Stan Black,<=-
 
Hi, Jeff;
 
 SB> I have made several yagis and quads for 2 meters.  I love antennas!
 
I love antennas, and I love playing (experimenting) with them!
 
 II> I do have an old CB SWR bridgs which I modified to be accurate on 2M.
 > ...
 JE> All those technical articles would be appreciated here, Ivy...  This
 JE> -is- after all, the HAM_TECH area 
 
Correctamundo!  That's why I pull it!
 
Any boy scout who can handle a soldering iron can do this one!   :-}
 
I have a dual-meter SWR bridge which was made for CB.  I haven't done
anything with CB for over 10 years, but I needed a SWR bridge for 2M.
So I proceeded to do the following:
 
There are supertech types who will dispute me on my method, but here is
how I modified a dual-meter CB SWR bridge to be pretty accurate around
150 MHz with reasonable sensitivity.  Do the same thing on both detectors:
 
  From directional     D1
  coupler:     --------|<-|------
                          |     |  Added mini pot, aprox 100K - 250K
(I could have done       ---    \
 a lot better if I    C1 ---    /
 had used high ASCII)     |     \
                        -----   / <--- To meter
                         ---    \
                          -     /
                                |
                              -----
                               ---
                                -
Modification: Add a mini pot, (salvaged from old equipment), of aprox
100 250 K or so.  Do this for both detectors.
 
Calibration: Feed the ANT side of the bridge into a load, (I used an
antenna with low SWR, but a 50 ohm dummy load would have been preferable).
Connect 2M HT to the XMTR side of the bridge.  Turn the bridge's CAL pot
to almost full sensitivity and apply RF from the HT.  Adjust the added
"Fwd power" pot for full scale deflection of the fwd power meter.
 
Then reverse the input and output RF connections to the bridge, (DO NOT
apply RF during this - DUH!), connecting the HT to the ANT connection,
and the load to the XMTR side.  Be careful NOT to change the setting of
the bridge's CAL setting during this procedure!  Again apply RF, and
adjust the added "Refl power" pot for full scale deflection of the SWR
(reflected power) meter.  The unit is now calibrated.  Reassemble the
SWR bridge and the modification is complete.  What could be simpler?
 
The modified bridge has since been checked using a known accurate 50-Ohm
dummy load, and the indicated SWR was aproximately 1.1:1, so it isn't far
from perfect.  (The 2-gang CAL pot in this particular individual unit
does not track very well, but it's plenty accurate for my purposes.)
 
-30-
 
And you're Welcome.   :-}
...
 
 II> I would LOVE to get my hands on the ARRL antenna book.
 
 JE> I've got an old 1950's version of it... GREAT info in there!
 
Want to get rid of it?  (Perhaps upgrade to a newer version?)  ;-}
If so, I would be glad to pay postage and maybe a few $$ for it if you
like.
 
73 DE KB9QPM
   Ivy
 
 
 
... Real HAMS do it till their Mega Hertz.
 
         --
 
          ,-----> Ivy's WALL BBS Ä Home of Lakeshore Net <-----,
          |---------------> Ivy Iverson, KB9QPM <--------------|
          `-> Netmail me a request for info on Lakeshore Net <-'
 
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