[amsat-bb] Re: New Lindy's QRV

Bruce Robertson ve9qrp at gmail.com
Mon Feb 8 18:42:52 PST 2010

Being omnidirectional, this antenna offers no gain, so preamps are, in
my opinion, absolutely essential (at least on 70cm).  Moreover, you
need to use one that has a proven low noise factor. For practical
purposes , this means SSBUSA or ARR models.

By way of contrast, note the reception of AO-51 in the second half of
this videohttp://www.youtube.com/watch?v=XgNcCGXeRyw It's not great,
but its better than you describe, and I'm doing it indoors, with a
silly wire dipole made out of #12 copper wire. However, it's directly
connected to a preamp, and that makes all the difference.

Similarly, all the 70cm work in my videos is currently conducted with
a 1/4 wave vertical connected directly to an N-connector, up about 20'
in the air, followed by 10' feet of LMR400 and a good low-noise
preamp. The reason I'm building the lindy is to even out the pattern
compared to the vertical, which, of course, has deep nulls overhead
and elsewhere in its elevation pattern. Despite that, HO-68's beacon
is audible Q-5 from horizon to horizon for me even with the 1/4 wave

While a preamp represents a considerable amount of money, the good
news is that the improvement from a preamp applies to any sort of
antenna you might use or build, at least those to which it is
convenient to connect a preamp.

73, Bruce

On Mon, Feb 8, 2010 at 8:26 PM, David Ek <dave at eksfiles.net> wrote:
> Question for anyone out there: I just built the parasitic Lindy from the
> Feb 2010 QST. What kind of performance (on receive) should I expect from
> it during, say, an AO-51 pass (max EL 83 deg)? I had my Kenwood TH-F6a
> HT connected directly to it (only a few feet of RG-8X coax to the
> antenna) with no preamp, and I only had good copy for a moment here and
> there. Just wondering if I need a preamp or if I need to be suspicious
> of my construction.
> tnx & 73,
> Dave NK0E
> -----------------
> Edward Cole wrote:
> I forgot to add that these are patterned after Tony, AA2TX, designs
> (UHF version is in Feb. 2010 QST).
> My variation was to use pvc sched-40 plastic pipe (white).
> The preamp is one of the older DEMI designs that uses a mgf-1302
> GasFet with about 0.7 dBNF.  I see about one s-unit of noise when I
> turn it on.  There is 4-feet of RG-58 to the UHF Lindy and 60-feet to
> the FT-847 from the preamp.  The VHF Lindy has no preamp and is fed
> with 60-feet of RG-213.
> The VHF Lindy brings up repeaters 70-miles away with 50w, and the UHF
> Lindy hears repeaters that far away.  So actually can make a nice
> general purpose antenna.
> 73, Ed
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