I originally ran a T6 from Tennadyne. It was ok on 10/12/15 but I was never
excited about the performance on 17 and 20. I am no EE but I figured the boom
length was probably a little short. I run an XR5 now and am very pleased with
the performance.
Phil
N9LAH
----- Original Message -----
From: "Gene Fuller" <w2lu@rochester.rr.com>
To: jim@audiosystemsgroup.com, towertalk@contesting.com
Sent: Friday, October 25, 2013 11:38:55 AM
Subject: Re: [TowerTalk] Tower and antenna decisions
Hi Jim -
Would you like to add any comments regarding LP's. Granted, only as much
"gain" as a good two or three element yagi and no killer as far as F/B is
concerned, but no traps, no "critical" tuning, only one feed line, one boom
and only one rotator. For that matter the TH-11 uses a small log cell, with
no traps for the "driven" element(s), and combined with parasitic directors
and reflectors, with relatively few traps, should be a fairly effective
antenna, as should be the Tennadyn LP's
Gene / W2LU
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <towertalk@contesting.com>
Sent: Thursday, October 24, 2013 11:26 AM
Subject: Re: [TowerTalk] Tower and antenna decisions
> On 10/23/2013 9:10 PM, Avery Davis wrote:
>> TH-11DX at 34 feet?
>> HexBeam at 50 feet?
>
> As to gain figures for these antennas -- around 1999-2000, Ward, N0AX, and
> Steve, K7LXC, set up and measured a dozen or so tribanders on a tower
> under carefully controlled conditions. A few years later, Tom, N6BT, did
> similar work. Both found that the CLAIMED gain numbers for all of them
> (except Tom's Force 12 designs) were wildly inflated, often by as much as
> 6 dB. Two antennas that Ward and Steve measured actually had NEGATIVE gain
> as compared to a resonant dipole at the same point. You can buy a report
> on their work from K7LXC's website. It's $20 well spent. Steve also sells
> N6BT's "Array of Light," which includes his measurements and lots of
> excellent discussions of various antenna designs. I think it was $35.
>
> One of the points that Tom made in his book (really a somewhat
> disorganized collection of essays he's published over the years) is that
> the most efficient antennas are simple monoband Yagis, and that when traps
> are added to cover multiple bands, the traps burn some of the transmitter
> power, and the shortened elements reduce radiation resistance (the part of
> the antenna impedance that accounts for radiated power), which also
> reduces gain. Thus, the gain of an ideal 2-element or 3-element Yagi is
> the BEST that can be achieved by an antenna with the same number of
> elements for that band. The advertised gain figures for the antennas that
> Ward, Steve, and Tom measured were 3-6 dB greater than for the ideal
> Yagis!
>
> I would look at one of lighter-weight antennas that does not use traps. My
> 3-element SteppIR (the original with no trombones) works very well, have
> been essentially trouble-free for the four years it's been up, and is
> lighter in weight than most other antennas you are probably considering,
> which makes it easier to install safely. It has the efficiency of an
> optimized single-band Yagi on all bands, including the WARC bands. With
> the added fixed 6M element, it's also a very good performer on that band.
> No, it's not cheap, but given your constraints, it's a very good choice.
> Even the simple 2-element SteppIR would be a good choice, and can easily
> be handled by one person. I learned that when I helped N6KJ assemble his
> for Field Day several years ago.
>
> I'd also look at the Force 12 antennas, none of which use traps, and which
> provide very good bang for the buck. The two that Ward and Steve measured
> were the best performers in both groups they measured -- small tribanders
> and larger tribanders.
>
> 73, Jim K9YC
> _______________________________________________
>
>
>
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