Hi Mike,
I was trying to address the particulars of N2IC's situation which
involved the higher HF bands (although at this point in the sunspot
cycle, perhaps I should have included 20 meters).
Reading the manual I have for the MFJ-1026 says "The MFJ-1026 is
optimized over the range of 1.8 to 30 MHz". Does the MFJ-1025 only go to
20MHz?
73, Mike W4EF........
On 3/17/2020 10:31 AM, Mike Waters wrote:
Mike, is there any reason why you tested it above 20 MHz? That's outside
the 1026's specified frequency range.
73, Mike
W0BTU
On Tue, Mar 17, 2020, 9:07 AM Michael Tope <W4EF@dellroy.com> wrote:
I just happen to have a spare MFJ-1026 at home. I did a real quick test
using my FT1000MP MK-V while powering the MFJ-1026 from an Astron
supply. Similar to your results, Steve, I got about a 12 to 14 dB
increase in the noise floor on 10 meters when the MFJ unit was turned on
and connected to the MK-V's main antenna input versus when the MFJ unit
was powered off. This suggests you would have to resort to having
low-noise pre-amps ahead of each of the MFJ-102x two signal paths and
the right amount of attenuation after the MFJ-102x's combined output to
work in your particular very low noise situation.
Since the main antenna path is normally bypassed for transmit, to put a
pre-amp ahead of the main antenna path you would have to either move
that MFJ-102x out of the transmit path by putting it in a receive-path
breakout-loop that is common on many modern transceivers (e.g. between
RX_OUT and RX_IN jacks), or you would have to have add a dedicated T/R
bypass scheme for the external main path pre-amp.
FWIW, I also made some gain measurement on my MFJ-1026 (both main and
sense path gain controls fully clockwise):
Main Antenna Path Gain:
10 Meters: 4dB
15 Meters: 3dB
Sense Antenna Path Gain (sense-path pre-amp on and internal jumpers set
for maximum gain):
10 Meters: 0.5dB
15 Meters: 1.6dB
Difference between having Sense Path Pre-Amp On vs Off:
10 Meters: 8dB
15 Meters: 9dB
I used an Elecraft XG3 as the signal source and an HP141T to measure
amplitude.
73, Mike W4EF...................
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