I recently bought a diamond 210 and when we got it put together, I found 
diamond has what I consider a main design flaw.  The last dual bander I 
had up was a comet, I don't recall the model.  I didn't realize until I 
got this last diamond.  I'll try and describe the problem.  At the 
bottom of the diamond right below the radials is a round piece about 2 
inches long and at the bottom of this is where the coax connects.  This 
piece sets inside a piece of tubing a foot and a half long and this 
piece is where the mounting hardware goes that mounts the antenna to the 
mast.  All that holds that hole top part of the antenna in place is a 
small bolt that goes through a hole in the pipe and screws into the 
round piece that slides inside.  Hope that makes sense.  The problem is 
(this happened to me 2 or 3 times in Vegas, is vibration shakes this 
bolt out and then the antenna just wobbles around inside this tubing. 
If they insist on mounting it this way, there should be bolts.  What I 
did to fix my uhf one in vegas was to cut an x or cross in the outside 
tubing with a hack saw and put on a hose clamp. This held the bolt in 
and also compressed the tubing against the inside part.  A poor design 
as far as I'm concerned.  Commit is totally different and much better. 
I'll never buy another diamond.
73
Butch
WA0VJR
Node 3148
Wallace, ks.


On Tue, 28 Apr 2015, Colin McDonald wrote:

> I've pulled a couple of these apart.
> There are multiple matching coils, loading coils and various element
> arrangements all the way up the antenna.
> It's not a simple thing to build.
> far easier to build a yaggie or quad for those bands.
> I expect it would also be more expensive to build something like the
> x200/300 as well than it is to buy one.
>
> 73
> Colin, V A6BKX
> -----Original Message-----
> From: Neil k8it
> Sent: Tuesday, April 28, 2015 2:24 PM
> To: [log in to unmask]
> Subject: Re: plans for high gain 2m 70cm antenna
>
> I have been thinking of building a base station 2m and 70cm antenna. I like
> the diamond x-200a or x-300a designs but would like to try building one
> myself. the antennas are rated at 6 to 6.5 dB on 2m and 8 to 9.5 dB on 70cm.
> But does anybody have dimensions of this type of antenna? I found several
> J-pole designs but no 5/8 wave collinear designs with radials similar to the
> Diamond x-200A or x-300A antennas.
> Anybody have any thoughts?
>
> Would a 8 foot center element (two 5/8 waves in series simply work? would it
> match to 50 ohm coax? will it match on 70cm?
>
> thanks
> 73 Neil k8it
>
>