Factory Tuned Antenna?????

[Watergate]

I've been looking for dual band VHF/UHF antennas, and have come across something I find interesting from Diamond Antenna.

Diamond SG7500A

It says:

Special Features:
• Factory pre-tuned, no adjustment
• Highest gain
• Wideband performance
• 24Kt gold plated connector pin

Does this really mean no adjustments for SWR are needed? Has anybody used one of these and would you trust them?

 

[Captain Kilowatt]

It is what it says, no tune. in fact i have not seen a dual band 2m/70cm mobile antenna that did need field tuning. If you attempt to tune them you usually optimize one band while screwing up the other. I have used the diamond SG series before as well as the Comet 2x4SR dual band no tune and they work great. In fact the Comet 2x4SR (made by NCG the same company that makes Diamond antennas) was designed for W I D E bandwidth to accommodate the 2m and 70cm bands as well as frequencies above and below those bands used for typical Search and Rescue operations hence the SR designation. BTW I have had my Comet 2x4SR for over 12 years and it still works top notch. I have no problem with buying/using Diamond or Comet (same basic manufacturer for both) for performance or durability. There was an issue many years with water ingress and a faulty fold-over base which has long since been overcome.

 

[Watergate]

Thank you much CKW.

Just when I thought I was getting a handle on this whole radio thing, something new always pops up.

 

[Captain Kilowatt]

I have been in it for 35 years both as a hobby and as a profession and I still encounter new stuff. It never ends.

 

[ahamoperator]

SG7900

Hello, I put the Diamond antenna in question on my XYL's car..well sort of...
built an extended feed mount for it that mounts to the tow-hitch location.

The antenna does say it needs no tuning and probably does'nt. But me being
who I am had to fine tune it...hi...There is inter-action on the two bands, just
like the Captain says, so be careful tuning it, or don't tune it is the best
advice really.

It has spots slightly lathe-turned down for the set screws on the elements, so
unless you are able to change that slightly you can't tune it...

The antenna is co-linear with a 1/4 over 5/8ths on 2m and supposedly 5/8
wave times three on 70cm if I remember right.

All that being said, I think this antenna has far out performed anything we've
used in quite some time, regardless of how it is mounted (or where)

The only shortcomings of the antenna I can see is it's durability. I have heard
complaints on the web of the first (lowest) coil coming apart. I have to say
it looks as if ours is loosening a bit, but still performing well. Make sured you
grip below the coil when folding it down for the garage.

We have an extreme QTH here and we can communicate at distances of up
to 50 miles in certain directions with just a co-linear vertical @ maybe 30 ft
running 50 watts. could'nt do it before.

73

 

[ahamoperator]

Diamond SG7900

Never posted a pic here before, hope it works...

 

[ahamoperator]

oops

Sri, guess I did'nt read the OP very efficiently.. 7500 not 7900...hi...