Original article from: Wayne Sarosi 
 Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo.
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SUBJECT: Wire antennas - part 5
RHOMBICS:
 I've talked about rhombics before and in this posting I would like to 
iscuss
the rhombic for use in the UHF range. We have hashed over rhombics in the HF
range and many antenna books discuss this antennas.
 Most AROs don't have the room on their property or do not have property to
construct a rhombic on.
 There seems to be very little on rhombics for UHF work.
 After looking at some plans for a multi-element rhombic on 70cm,I decided to
modify the plans and came up with a 23cm,12 element rhomboid.
 The official name is: dual hexamerous rhomboid which is 2X6 rhomboid 
ntenna.
 The antenna has twelve elements,with a gain of 33dBi,and is no bigger than a
TV antenna! On 70cm,the antenna is 19-ft long (apprx) and below that I would
not bother unless you have the tower and room.
 Unless you can mount a B-52 to a tower,2m is out of the question.
 Testing on the 23cm DHR shows a Front to back ratio greater than 30:1 with
front to side ratios about the same. This is a true cannon.
 The main lobe is tight at 12 degrees both vertical and horizontal.
 Matching is a bit difficult since micro-strip knowledge is a must.
 Although the antenna is 50 ohms balanced,the frequency demands exactness.
 This involves phasing elements,stripline baluns,and hardline feeds.
 But for the 23 experimenter,this antenna packs the punch of a large 
arabolic
reflector and in a small package.
 I'll be giving the details in the next posting.
-WS
--- GoldED 2.42.G1219
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