New Base Antenna – Diamond X300A Dual Band

The most important part of my home amateur radio station is finally in place!  Here is my Diamond X300 antenna, installed about 5 feet above the roof, top of the antenna at 56 ft above sea level.

Diamond X300A Dualband Base/Repeater Antenna  Diamond X300A Dualband Base/Repeater Antenna  Diamond X300A Dualband Base/Repeater Antenna

Click thumbnail to view full size image

My Antenna Setup:

Diamond X300A Assembly Notes

The antenna is fairly easy to assemble using a few basic tools.  Be sure to carefully read the Diamond X300A instruction manual (PDF) at least once. I applied dielectric silicon grease to the weather gasket to ensure reliability and also to the internal element joint bracket to prevent possible oxidation in the joint.  I then attached the upper element to the lower element very securely with a #2 Philips screwdriver, assembled the upper and lower shell pieces tightly, wrapped the entire joint with silicon self-fusing tape, then finished with a final wrap of good 3M electrical tape.  While wrapping with silicon tape may not be necessary, I wanted to ensure a long-life, weatherproof joint.  Finally I applied dielectric silicon grease on the radial element joints to prevent corrosion, then tightened well.

Diamond X300 antenna assembly  Diamond X300 antenna assembly  Diamond X300 antenna assembly

Coax Preparation and Antenna Installation

It’s been close to 10 years since I installed PL-259 connectors but the technique came back quickly.  LMR-400 coax is tough stuff; peeling and scraping the aluminum outer shielding, bonded (glued?) to the inner conductor insulator, was a pain in the ass.  My trusty razor knife came through.  Twist the PL-259 down on the coax with a pair of pliers, nip the tip off the center conductor, solder that sucka good.  Finally slid a piece of super mega duty, dual-wall heat shrink over the back of the connector and heat it up/shrink it down for a permanent seal and coax strain relief.

I filled and weatherproofed the connector with “Stuf” dielectric compound.  Connected the coax securely to the antenna.  The coax slips inside the antenna support pipe so space was tight, so I wrapped the connector with Vipar X-Treme self-fusing silicon rubber tape (instead of the more bulky Coax-Seal), then a quick wrap of good 3M electrical tape to make sure the silicon tape can’t unravel.  These little details should hopefully keep the weather out and ensure reliability for years to come.

Finally, finish bolting everything together and test the antenna.  VHF SWR is 1:1 to 1.2:1 across the 2 meter ham band.  I was unable to test UHF due to a faulty meter; however, actual on-air performance is excellent.  I do intend to test and monitor SWR when I get a new meter.

Diamond X300A Antenna Performance @ 50 Watts

Under normal conditions I can reach repeaters up to 45 miles away, albeit with noisy signal.  I can talk comfortably on 2 meter up to 35 miles and 70cm up to 37 miles.  I receive less static noise on 70cm; unfortunately there is not much local activity on the 440 band.

My home is located “down in the hole” at 27 ft above sea level (find your elevation here).  There are hills to my north and east rising to around 120 ft. within a mile of my home, which makes distance contacts in those directions more difficult.  That being said, I can reliably talk on a repeater 31 miles to my north at 1,000 ft. elevation. Locations south and west, especially across the Chesapeake Bay and down into Baltimore and Annapolis are no problem.

I am very pleased with the Diamond X300 and I highly recommend it!

Comments

  1. John Markham, KD6VKW November 20, 2016 at 8:56 PM

    I have one of these that a friend asked me to make ready for use. The radials are gone, but the female threads are still good, So, I plan to make him some new radials, probably attaching them with S/S machine screws, rather than threading them.

    How long should I make them? I figure it matters. (On your photo, I observed and measured the ratio of the radial to the lower section as 0.42 Here, the lower section measures 55 inches, making the radials be very close to 24 inches long.)

Leave a Reply

Your email address will not be published.

Name *
Email *
Website