I didn’t word that quite right. I don’t intend to mod the SP-75. Just the ends of the cable connectors.

— Steve, W?PZ

--
Steve? W0PZ

It's another brand of antenna tuner made by Murch Electronics.

Did the SP-75 originally come with 4-pin XLR connectors?

If so, are there any “gotchas” in converting to TRS on both sides so as to plug a Shure 444 in one side of the SP-75, and plug in to a T-4XC on the other side (I’m concerned about matching the Shure cable impedance, etc).

The Shure 444 uses TRS and so does the T-4XC.

I’m trying to do this in such a way that I do not cut my original Shure cable, but that means I (probably) have to locate a short additional Shure cable.

—Steve, W?PZ

--
Steve? W0PZ

At the appearance of being incredibly dumb, what is a 'Murch'?
Joe - W7RKN

I have several tuners, including the Murch.? It was popular because the roller inductor Ultimate Transmatch had huge popularity in the late

'70s.

In the end, that roller was a pain, and not really neccessary. The Swan tuner with a tapped inductor became my favorite!

....Dave

This is the tech behind the Murch. And also why you find homebrew variants.



73

-Jim
NU0C

On Sun, 21 Mar 2021 13:22:00 -0500
"AC9PA via groups.io" <byroncordes@...> wrote:

Well if where talking tuners ! Ten Tec L tuner works but cost is high .

On Mar 21, 2021, at 12:48 PM, Jim Shorney <jshorney@...> wrote:

?
I was just thinking the same thing. I have a Murch sitting atop my MN2700. And a second homebrew knockoff awaiting cleanup. Spent less money than a night on the town for both combined.

73

-Jim
NU0C

On Sun, 21 Mar 2021 16:45:41 +0000
"Dick" <w1ksz@...> wrote:

Look for a Mutch UT-2000B (not the A). They go for short money
and will load up the proverbial bedspring.

73, Dick, W1KSZ
________________________________
From: [email protected] <[email protected]> on behalf of Billy Pickering KO4INE <pickeringw@...>
Sent: Sunday, March 21, 2021 9:16 AM
To: [email protected] <[email protected]>
Subject: Re: [DRAKE-RADIO] MN2000

We have a huge hamfest coming up this next Saturday in Sevierville that I'm going to keep an eye out there and see what I can find. Thanks everyone.

I found a nice little Drake PRN 1000 locally. Nice rich sound and looks good too. Only paid $100.00 for it. Nice add to my twins.

Good point on the resistor values. I had to increase them substantially for my blue display.

73

-Jim
NU0C


On Sun, 21 Mar 2021 14:32:11 -0400
"Joe Pyles" <epyles@...> wrote:

Multiplexed means that each of the seven segments of each display is
connected to the same segment of all of the displays. The segments
for a given number is turned on and then the correct digit is turned
on. The digits are turned on one at a time and this happens fast
enough that your eyes perceive them to be on at the same time. By
using this method you only need one decoder driver chip instead of
six that you need for a non multiplexed display. It was done to
reduce the size and parts count in the counter. The original
resistors were for ballast on each LED Segment and they were 33 ohm.
I used the DF4NW .3" Display and the LEDs were way too bright and
rather than use a dark filter to tame the brightness I replaced the
original 33 ohm with 470 ohm resistors. The advantage to the larger
resistors is to both dim the display and promote much longer LED life.


[]


73, Joe Pyles KC9LAD

At 01:56 PM 3/21/2021, you wrote:

Thanks Joe
By multiplexed do you mean the bank of resistors (I think 100k)
going between the KHz segment and the Mhz?

Will look at those as well.



Kind Regards
Mike
G3ZCC

Multiplexed means that each of the seven segments of each display is connected to the same segment of all of the displays. The segments for a given number is turned on and then the correct digit is turned on. The digits are turned on one at a time and this happens fast enough that your eyes perceive them to be on at the same time. By using this method you only need one decoder driver chip instead of six that you need for a non multiplexed display. It was done to reduce the size and parts count in the counter. The original resistors were for ballast on each LED Segment and they were 33 ohm. I used the DF4NW .3" Display and the LEDs were way too bright and rather than use a dark filter to tame the brightness I replaced the original 33 ohm with 470 ohm resistors. The advantage to the larger resistors is to both dim the display and promote much longer LED life.




73, Joe Pyles KC9LAD

At 01:56 PM 3/21/2021, you wrote:

Well if where talking tuners ! Ten Tec L tuner works but cost is high .

Strobing or multiplexing of LED displays is a common method of reducing parts count and average power consumption. Have a look at the schematic. Resistors R9077 through R9083 are the current limiting resistors for the segments. Segment data for each digit is clocked sequentially into the segment driver U9032 by the counter circuitry. In step with that the anode of the correct digit is powered at the proper time by transistors Q9005 through Q9010. So each digit lights in turn with the proper segments lit at the proper time but is dark for the rest of the cycle. This all happens very fast so you don't see any flicker with your eyes.



73

-Jim
NU0C



On Sun, 21 Mar 2021 10:56:23 -0700
"Mike Davidsohn G3ZCC" <mike@...> wrote:

Thanks Joe
By multiplexed do you mean the bank of resistors (I think 100k) going between the KHz segment and the Mhz?

Will look at those as well.

Kind Regards
Mike
G3ZCC

In my experience the only area of the DR7 that is prone to shorting is the left rear corner where a set on Moolex pins reside. It's possible to push it down too far. I solved that problem with some flat stick-on rubber feet on the bottom of the board.

73

-Jim
NU0C

On Sun, 21 Mar 2021 10:53:55 -0700
"Mike Davidsohn G3ZCC" <mike@...> wrote:

Hi Gary

Funnily enough I made a strip out of clear acrylic which I put on the shelf where the? bulb clips on.

Also put one over the lower level cover and cut out holes for the wires etc.

By bad foil do you mean a strip of printed circuit that is ground?
Will check those out too.

Thanks for the tips.

Kind Regards

Mike G3ZCC

More likely it is a broken trace than anything else. The display board is a nasty bugger to unsolder. The LEDs are a standard off the shelf pinout, you could replace them if bad. Not that I am discouraging you from sending DF4NW some money, he is a good guy. I bought the first blue display in the original LED size from him. Since I had already changed the ALC lamp to blue I had the first all blue TR7 in the world, a claim that has not been challenged to this day!

73

-Jim
NU0C

On Sun, 21 Mar 2021 10:49:07 -0700
"Mike Davidsohn G3ZCC" <mike@...> wrote:

Hi Jim

Managed to repair one of the spare PTO's all fitted back and seems to be? working ok.

Not putting the front back as I am changing the bulbs to blue LED's.

Then to the DR7 will check through again, thanks for the tip on checking the segments, will do that tomorrow.
If those LED's have a problem I will check out DF4NW to see if I can get a replacement.

Hoping it's just a solder joint.

Kind Regards

Mike

G3ZCC

Thanks Joe
By multiplexed do you mean the bank of resistors (I think 100k) going between the KHz segment and the Mhz?

Will look at those as well.

?

Kind Regards?
Mike
G3ZCC

My Murch is green. But it's not a "B" model. Someone had butchered it with cheapo verniers that were worn out. I actually found a pair of period correct knobs molded in green plastic to restore it with. It looks ... interesting. :) And I really don't care that it doesn't match the rigs.

It should be noted that early designs did not have a bypass switch, which is not a big deal for a single band use antenna that needs it.

73
-Jim
NU0C

On Sun, 21 Mar 2021 10:22:00 -0700
"VE7PS" <ve7ps@...> wrote:

Someone mentioned the Murch tuner - it's black - wouldn't look bad at
all next to a 4-line.

Hi Gary

Funnily enough I made a strip out of clear acrylic which I put on the shelf where the? bulb clips on.

Also put one over the lower level cover and cut out holes for the wires etc.

By bad foil do you mean a strip of printed circuit that is ground?
Will check those out too.

Thanks for the tips.

Kind Regards

Mike G3ZCC?

I ment the MN-4C, I don't know why I said the MN-2000C......

I've looked at the Murch tuners as well.

Hi Jim

Managed to repair one of the spare PTO's all fitted back and seems to be? working ok.

Not putting the front back as I am changing the bulbs to blue LED's.

Then to the DR7 will check through again, thanks for the tip on checking the segments, will do that tomorrow.
If those LED's have a problem I will check out DF4NW to see if I can get a replacement.

Hoping it's just a solder joint.

?

Kind Regards

Mike

G3ZCC

I was just thinking the same thing. I have a Murch sitting atop my MN2700. And a second homebrew knockoff awaiting cleanup. Spent less money than a night on the town for both combined.

73

-Jim
NU0C

On Sun, 21 Mar 2021 16:45:41 +0000
"Dick" <w1ksz@...> wrote:

Look for a Mutch UT-2000B (not the A). They go for short money
and will load up the proverbial bedspring.

73, Dick, W1KSZ
________________________________
From: [email protected] <[email protected]> on behalf of Billy Pickering KO4INE <pickeringw@...>
Sent: Sunday, March 21, 2021 9:16 AM
To: [email protected] <[email protected]>
Subject: Re: [DRAKE-RADIO] MN2000

We have a huge hamfest coming up this next Saturday in Sevierville that I'm going to keep an eye out there and see what I can find. Thanks everyone.

开云体育

Billy:

An MN-2000C?? Never heard of this one and I thought I knew of all the Drakes including the commercial marine reserve gear.? There is an MN-4C for sure (have one) which looks like an MN-7, but matches the 4-line, though not as well as the MN-4/MN-2000.

Someone mentioned the Murch tuner - it's black - wouldn't look bad at all next to a 4-line.

73
Peter
VE7PS