MFJ collinear array - elmers Forum at eHam.net

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MFJ collinear array	Reply
by K9FON on November 19, 2009	Mail this to a friend!
I just got a MFJ collinear array today from R&L. Yeah I know, I "bought" a wire antenna (old hams are spinning in their graves as I type! LOL) but my question is, can I use the antenna with my tuner for 40 meters? It is made for 20 but is the lenth of a 40 meter dipole..

RE: MFJ collinear array	Reply
by AA4PB on November 19, 2009	Mail this to a friend!
Not with the shorted stub matching section still attached. The feed impedance (full wave center fed) is high on 20M and the stub matches it to 50 ohms. On 40M it will be 1/2 wave and the feed impedance will be low (near 50 ohms) without the matching stub.

RE: MFJ collinear array	Reply
by K9FON on November 19, 2009	Mail this to a friend!
well i guess if i get bored i can always remove the feedpoint, solder on some more 450 ohm ladder line, run it to the tuner and turn it into a 40 meter doublet.

RE: MFJ collinear array	Reply
by K9FON on November 20, 2009	Mail this to a friend!
What kind of performace should i expect from the 20 meter colinear on 20 meters?

RE: MFJ collinear array	Reply
by W8JI on November 21, 2009	Mail this to a friend!
[quote author=K9FON link=topic=63880.msg413450#msg413450 date=1258783671] What kind of performace should i expect from the 20 meter colinear on 20 meters? [/quote] How long is it? In some cases with twinlead or ladder line feed, the gain is very close to 0 dBd. What can happen is feedline loss caused by the very high SWR on the ladder line offsets the collinear gain, so the overall thing is a wash. For example I put up an 80 meter extended double zepp antenna here and the actual gain, once I included the 450 ohm line losses, was just over 1 dBd. I had to get away from ladder line and use a coaxial fed collinear to get near full gain over a dipole. Tom

RE: MFJ collinear array	Reply
by AA4PB on November 21, 2009	Mail this to a friend!
You can feed it with ordinary ladder line and a balanced tuner if you want it to operate on 40M and above. If you only want to use it on 40M then feed it with coax directly. Its also possible to add a pair of 20M traps and feed it directly with coax on both 20M and 40M. For a normal installation I seriously doubt that you will be able to tell the difference between the 20M collinear and a standard 20M dipole as a practical matter.

RE: MFJ collinear array	Reply
by W8FR on November 21, 2009	Mail this to a friend!
Hello, The MFJ62xx and 61xx series of aerials are "single-band aerials when the shorted-stub is intact. If you want to use it on other bands (not really recommended), open the short, disconnect the coax from the SO-239, and continue the lsdder line into your shack to a fully-balanced tuner... It will still perform on 20m (if you are using a MFJ-6220) as a 2 element collinear, and "whatever" on other bands like a so-called "center-fed Zepp..." Note: A classic Zepp is ONLY fed at the end of the halfwave; no such thing actually as a center-fed ZEPP; misnomer We designed/proto-typed these aerials in 2005 as single-band, "Hang N' Play" antennas as explained in the catelog, and on "Antenna Talks" a link at the upper-left hand of MFJ homepage; select #1 for a detailed description of the merits/demerits of the aerial. 73 De W8Fred Race

RE: MFJ collinear array	Reply
by W8JI on November 21, 2009	Mail this to a friend!
The article at "antenna talks" has a few problems. I'd stay away from it and use the handbook or something. Tom

RE: MFJ collinear array	Reply
by W4VR on November 21, 2009	Mail this to a friend!
I use a coaxial fed co-linear dipole array on 17 and it works like a charm...that pattern is similar to that of an extended double zepp. And, it also works with low SWR on 12 meters. I have not modeled it on 12 but I should, to find out what's going on there.

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