Wednesday, April 14, 2010

Shootout on Tallentire Hill

It has been a glorious day today. After lunch I set off for Tallentire Hill armed with the TH-205E and three antennas: a 2m telescopic quarter wave, a 45" 2m 5/8 wave Black Whip telescopic from eBay seller jeepbangkok and the SOTA Beams MFD.

I set up the MFD in the vertical position strapped to a fence post and put out some calls. Despite my high elevation the 2m band was quiet and I only managed to raise "the usual suspects". Richard MM1BHO/M heard me calling through the GB3DG repeater and we had a short QSO. Then Keith G0EMM heard me call on 145.500 MHz and was willing to spend a bit of time doing some antenna tests.

Prior to this I had heard a contact on the GB3CS repeater and had quickly swapped all three antennas to see what the difference was on receive. There was no noticeable difference between the MFD and the Black Whip but both were significantly superior to the 1/4 wave telescopic (which is itself an improvement over the short whips and "duckies" normally used with 2m handhelds.) However the signal was steady on the MFD whereas it varied depending on the position in which I was holding the TH-205E with the BNC mounted antenna. When using the MFD I was sitting on the ground so it was above my head and my body wasn't interfering with reception. When using rig-mounted antennas it is best to stand up as an extra couple of feet above ground make a noticeable improvement. But it is also worth turning around and moving a short distance as the direction you are facing can make a big difference to signal strength.

Keith confirmed that there was no difference in my signal between the MFD and the 5/8 telescopic. I was 59 on both of them, whereas I was only 4 by 3 on the quarter wave. Keith also gave me my second unsolicited complimentary report on the TH-205E audio, saying it was "just like my voice." I was using one of the cheap Kenwood speaker mikes which I bought on eBay originally for the TH-F7E.

We were then joined by Colin 2E0XSD who again said that I was the same strength, 59+ on both the MFD and the 5/8 wave. I was only 4 by 7 on the quarter wave.

After I finished the contact with Keith and Colin I tried some more calls. I was able to access the GB3CS repeater using the MFD and the 5/8 - when in the right position - but not with the quarter wave. Some repeaters I could hear but not access even with 3W, which is what the TH-205E appears to put out on "high power" with the 7.2V battery pack, but perhaps they don't respond to 1750Hz tone-bursts.

When I bought the Black Whip a few weeks ago I put it on the antenna analyzer and got this SWR curve. I seem to remember that I had to collapse the topmost section to get the SWR null spot on 145.000 MHz but I don't suppose it makes any difference in practise.

I think the Black Whip 5/8 telescopic is a superb antenna for 2m FM use and well worth the few pounds it costs, as long as you have a radio that can handle it. The base is sprung to absorb any shocks but even with the HT Saver SMA to BNC adapter I was a little uncomfortable using it on the tiny TH-F7E. The big old TH-205E has no such problems with a large antenna, although its lower power output with the battery pack I have is a slight disadvantage.

Is it worth carrying the MFD instead of the 5/8, which telescopes down to the same length as a quarter wave telescopic antenna? Well, if you are using a modern hand-held radio then the MFD's coaxial connection will avoid putting undue strain on the SMA connector. You can secure the MFD to a fence post or stuff the support mast in your rucksack allowing you to operate sitting down and even let go of the radio when receiving. The MFD is also convertible to a horizontal dipole for SSB use. So it still has several benefits. But I expect I will be taking the Black Whip on most of my hilltop outings.
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