MFJ-956 - any good?
bpnjensen
a winner or otherwise? I notice CW has a mod on his webpage - can CW
or someone tell us what improvement that mod makes?
Thanks in advance for any input...
Bruce Jensen
CW
an interest in it and he was emailing the plans to people so I posted it to
take the load off him. I don't own one off these units and haven't done the
mod. I suppose he won't mind me posting his email address. fcat...@aol.com
He would be the one to talk to.
--
CW
KC7NOD
Web Page: www.kc7nod.20m.com
"bpnjensen" <bpnj...@yahoo.com> wrote in message
news:37af7e1c.02093...@posting.google.com...
katekebo
The results depend greatly on the receiver and the antenna system you
use, as well as your expectations.
I used the 956 with a 15 m MLB and a Lowe HF-150. It worked OK
eliminating 2nd order intermodulation. But it was not selective
enough to make this antenna work with a Sony 7600G. Not enough
attenuation of off-band signals so the Sony was still suffering from
overload. I also felt that it had too much insertion losses.
Eventually sold it to a guy who uses it with a JRC NRD-345 to get rid
of MW interference and he is quite happy with it.
The MFJ-1046 is more selective (attenuates more off-band signals) and
has less insertion losses. It works fine with both the Lowe and the
Sony.
There is a lot of misconception about how preselectors work and what
they do for your radio. It would be helpful if you could explain what
is your problem and what do you expect the preselector to do.
bpnj...@yahoo.com (bpnjensen) wrote in message news:<37af7e1c.02093...@posting.google.com>...
RHF
The MFJ-956 is MFJ's 'basic' Antenna Tuner.
* Low Cost (New ~$45 & eBay Used ~$30)
* Simple Design
* Good Build Quialty
* Small Size
* Easy to Operate
The only real way of finding out if an Antenna Tuner will work with
your radio equipment and you current antenna(s) is to Try It Out.
Borrow or Buy One and Use It. Test and Determine for yourself.
+ + + Some people find that an Antenna Tuner really hepls them out and
solves alot of their receiving problems.
= = = Other people find that the Antenna Tuner makes no difference.
- - - A Few people find that an Antenna Tuner makes reception
worse(r).
~ RHF
= = = bpnj...@yahoo.com (bpnjensen) wrote in message news:<37af7e1c.02093...@posting.google.com>...
> Hi, folks - anyone have any experience with the MFJ-956 tuner? Is it
RHF
I took a look at your link for the MFJ-956 Tuner Enhancement
(Modification).
The MOD looks interesting and well worth the effort for the
improvement achieved in the MFJ-956.
If you 'add' the Original text from Frank's posting to this NG it
would help to clarify the nature and extent of the MOD.
=QUOTE=
From: Fcathell (fcat...@aol.com)
Subject: MFJ-956 Tuner Enhancement
Newsgroups: rec.radio.shortwave
View: (This is the only article in this thread) | Original Format
Date: 2001-01-29 16:03:51 PST
For those of you using the MFJ-956 Tuner and a long wire who are not
entirely
satisfied with its performance, here is a mod that will improve its
shortwave
performance w.r.t. intermod and effective tuning Q. As designed the
tuner
works OK for the longwave band but at higher freqs. (> 2MHz) the
series
resonant tuner becomes problematic because the impedance of the series
L/C
approaches the input and/or output impedances and the Q is so poor its
performance is marginal to none depending on the length of the antenna
used and
its overall configuration. The existing bandswitch is a double-pole,
six
position with only one of the sections being used so one can take
advantage of
the other section to switch in some additional inductors that modify
the
antenna's input impedance. You will need to get a 1 uH, a 6.8 uH, and
a 100 uH
RF choke (Mouser Electronics and probably Radio Shack in one of their
"grab
bags"). The values aren't critical but should be within 20% or so.
The
"RECEIVER" and "ANTENNA" (input and output) ports will have to be
reversed also
so the tuning cap is on the output (rcvr) side.
Further improvement can be made on the LW range by changing the 2.5 mH
choke to
a 4.7, 5, or 6.8 mH choke. This will extend the lower end down to
the
specified 150 kHz for antennas less than 100 feet.
If you are interested in this mod please E-mail me and I will send the
schematic to you.
Frank
=UN-QUOTE=
A Search of this NG for MFJ + 956 + MOD yeilded the above post.
(Sorry NG Links are to long and truncatable.)
~ RHF
= = = "CW" <clinton...@attbi.com> wrote in message news:<Edam9.268227$Jo.124075@rwcrnsc53>...
Fcathell
Grove TUN3. This is where I got the idea for the mods to the MFJ-956. The
TUN3 occasionally shows up on E-Bay and is worth $40 or so. I still have mine
and it still is great for eliminating IM problems and "peaking" the signals for
some antenna configurations. It's almost a must if you a using less than 250'
of wire for LW. The MFJ does a pretty good job without mods on LW and MW but
has insufficient inductor Q for severe SW problems.
Frank
bpnjensen
> I used it for some time, then sold it and replaced it with a MFJ-1046.
> The results depend greatly on the receiver and the antenna system you
> use, as well as your expectations.
>
> I used the 956 with a 15 m MLB and a Lowe HF-150. It worked OK
> eliminating 2nd order intermodulation. But it was not selective
> enough to make this antenna work with a Sony 7600G. Not enough
> attenuation of off-band signals so the Sony was still suffering from
> overload. I also felt that it had too much insertion losses.
> Eventually sold it to a guy who uses it with a JRC NRD-345 to get rid
> of MW interference and he is quite happy with it.
>
> The MFJ-1046 is more selective (attenuates more off-band signals) and
> has less insertion losses. It works fine with both the Lowe and the
> Sony.
>
> There is a lot of misconception about how preselectors work and what
> they do for your radio. It would be helpful if you could explain what
> is your problem and what do you expect the preselector to do.
Hi - Well, I understand the basic difference between a tuner and a
preselector. The tuner "adjusts" the antenna configuration to the
best resonance at a given frequency; whereas the preselector acts more
as a "filter." I just wanted something that would help to make the
antenna more resonant for specific frequencies across the HF band (for
example, make a 60-foot random wire a bit more appropriate for 60m),
and maybe less resonant for adjacent frequencies. If that didn't
work, I might try a preselector, but what I really want to do is the
get the most out of a short wire for tropical bands. Neither of my
antennae at this time are very good for these frequencies, and without
a couple hundred feet for a run, I want to try other alternatives.
Bruce Jensen
Fcathell
resonant bandpass filters with a (hopefully) reasonably narrow bandpass at the
turned freq. Most antenna tuners are parallel resonant and typically
configured as "L" networks which are low pass filters or "T" networks which are
high pass filters. I think the latter are really better suited and designed
for xmtrs rather than receivers.
Frank
RHF
I guess my Grove Mini-Turner TUN-3 that I Won on eBay at $18 is a
Keeper. :o)
I also like the Yaesu FRT-7700 and the FRA-7700 for their LW and MW
Bands frequency handling besides their SW capabilities. Have you used
either of these?
~ RHF
= = = fcat...@aol.com (Fcathell) wrote in message news:<20021001111451...@mb-ch.aol.com>...
Fcathell
have been broken. The TUN3 has been the only commercial receiving antenna
"tuner" that has really impressed me. Bob Grove is a pretty clever designer
anyway. Most of his stuff is simple but effective.
Frank
starman
The passive preselectors I've built used a *parallel* resonant circuit
between the receiver's antenna input (unbalanced) and ground. The
preselector shunts all frequencies to ground other than the desired
(tuned) one, which is passed to the receiver.
*****
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starman
What kind of inductors are used in the TUN-3? Do they have ferrite
cores?
*****
Fcathell
between the receiver's antenna input (unbalanced) and ground. The
preselector shunts all frequencies to ground other than the desired
(tuned) one, which is passed to the receiver.>>
This will work too and may have the advantage of less throughput loss than the
series resonant one at higher frequencies if you are using multiple winding for
Z matching. The Grove and MFJ units use ferrite core RF chokes for the coils.
The one for the high end of the shortwave band is only a few uH so it may not
have any core at all. Despite the simplicity and the use of cheap RF chokes
the Grove unit is a very effective performer.
Frank