Well I have been back to work this week and the blog has suffered for it,I thought it would be easy to find time, but no, always something else to do, anyway I snuck out early today and have run the errands and am now in the shack playing with my recent eBay aquisition, an MFJ HF Analyzer.
I wanted to find out where the long wire is resonant, if anywhere, it's currently only around 20 something metres long with 1/4 wave counterpoises in the loft for 80/40/20 and 10m, this is all connected to a 9:1 unun and 50 ohm RG58 coax.
Well the wire on the bands has an swr of around 4:1 to 5:1 - no good for the internal ATU on the TS-480 but well in the range of the MFJ, so I hooked up the analyzer to my antenna switching box, through the ATU and to the long wire, thus meaning I could use the tuner to log the manual settings using the analyzer set to mid band frequencies.
It didnt take long, I have sets of TX,Inductor and antenna settings on the ATU for mid point on each band, giving <2.1:1 SWR at the band edges, with around 1.2 mid band.
80m was harder to tune with a narrower bandwidth, with 160m being impossible to tune.
As an experiment I tried my CB 5/8 vertical, a Sirio 827, and could tune that down to 80m also, this was harder overall to tune with a narrower bandwidth than the wire.
I also found that altering the inductor setting one click aside of the best setting would make the swr worse, but increased the 'useable' bandwidth, I shall have to look into the theory I think.
Hello Paul, Glad you are getting somewhere with the antennas and have some workable SWRs. All that technical stuff does my head in and accounts for my waiting nearly 25 years to take the (easier) Foundation Licence! Looking forward to see your shack Monday afternoon. Put the kettle on about half two!
ReplyDeleteI can understand how working must get in the way of the blog and things. Oh well, you don't need to update every day or so. Some blogs I read only get updated every two or three weeks and they are no less readable for it, so don't worry.
Bye for now, Adam
Hi Adam, I have studied the theory many many years ago but somewhat forgotten due to job circumstances, see you on Monday, I am looking forward to it, am out in totnes at the moment on my mothers laptop after a sesh at the seven stars and a curry taxis due at 00.00 hrs back to torquay, i cant wait for my license like you would not believe, can you get onto cb frq's at all 27 mhz..?
ReplyDeleteI got a MFJ analyzer from eBay as well, one of the best things I ever bought for the hobby. Last summer a friendly chap with a CB came at my house asking if had a SWR meter to tune his DV27 on the car. I told him I had something better, you should see his eyes when I tuned his antenna right on channel 20 within 2 minutes :-) Well I had a MFJ 949 in the past and had the same experience as you have. Very narrow bandwith. Now I have a (decent) palstar tuner which is capable to tune 1200W. It's easier to tune and the bandwith compared to the MFJ is 3 times larger. But well it's a little overprized compared to the MFJ. 73, Bas
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