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Author Topic: Recently purchased a Johnson Matchbox...  (Read 3487 times)
K9SRV
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Posts: 121




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« Reply #15 on: August 07, 2012, 08:12:50 PM »

Thanks to all you guys for the input.
I will get a closer look at my trees and try to estimate how high
I can git er up... Would 35-40 feet be only marginal?
Should I do everything I can to get to 50 feet? I was thinking
I could buy a crappy fishing pole, climb up about 20-25 feet
and affix that to the tree... Hopefully, that would be high enough
to work OK... BTW the Matchbox is the Lite, or rated for 300 watts AM.
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K0ZN
Member

Posts: 1547




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« Reply #16 on: August 08, 2012, 04:59:26 PM »

 You will have excellent results at 40 ft.  It is all RELATIVE !!!  Relative to how much money you want to spend to elevate the antenna !

 In "normal" ham operation you will have very good results at 40 ft.  That is a very adequate height.  Maybe this info will help! (chuckle....)  At 10 ft. high it will be horrible but you can make contacts.  At 20 ft. High it will work "useably", but not be great. You will be very pleased at the results at 40 ft. ....at 50 ft. it is very marginally better.   75 ft. is "wonderful"....  at 110 ft. high it will be a stunning performer.  Strung between two towers at 190 ft. it will be absolutely Killer for DX but maybe NOT so good for
local and regional contacts!  .... Again, it is RELATIVE: this is a HOBBY.....  My CFZ is at 40 ft. and I work all kinds of DX and get excellent reports on the lower bands.
It is NOT a great DX antenna on the low bands, although it is fairly easy to work Europe on 80 CW....but that is to be expected at 40 ft. is "LOW" on 80 M. State side
operation on 80M is very good.

Dig out an ARRL Antenna Book and look at the radiation plots of antennas at various heights.  It will be educational.

FYI: That 300 watts back then was assuming 100% modulated AM phone.... which will conservatively translate into 1,000 W in SSB service.

73,  K0ZN
« Last Edit: August 08, 2012, 05:02:44 PM by K0ZN » Logged
K9SRV
Member

Posts: 121




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« Reply #17 on: August 09, 2012, 03:56:13 PM »

Thanks much. I think 40 feet will be doable, 190' would mean
a midnight knife in the heart... Undecided
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W8JI
Member

Posts: 9296


WWW

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« Reply #18 on: August 09, 2012, 09:52:39 PM »

Thanks to all you guys for the input.
I will get a closer look at my trees and try to estimate how high
I can git er up... Would 35-40 feet be only marginal?
Should I do everything I can to get to 50 feet? I was thinking
I could buy a crappy fishing pole, climb up about 20-25 feet
and affix that to the tree... Hopefully, that would be high enough
to work OK... BTW the Matchbox is the Lite, or rated for 300 watts AM.

I have, and use on occasion, several KW matchboxes and one 300W matchbox. For example, here is data taken with one of my KW Matchboxes:

http://www.w8ji.com/balun_test.htm#Ladder_Line_Voltage_and_Current_tests

if that link won't work this way in look here at the page bottom:

http://www.w8ji.com/balun_test.htm

I can say with absolute certainty they do have very limited matching range compared to T network tuners, and you can run into many combinations they will not match. The fix is relatively simple, just alter the feeder length.

Planning antenna and feeder ahead is a good idea.

The biggest problem I have with stranded copperweld ladder line is rust. Get any water in the line, and the conductors can rust through. Loss is generally not significant, unless the line is wet. Wet operation is better with real air insulated line. 

73 Tom
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