Galaxy SSB Echo D9 mod question

[Hawkeye351]

Hi everyone,
Got a Galaxy SSB Echo (another one) on the desk. As was the first one, and an Excalibur I had, this one presents low receive (ambient noise, noise floor) also. After I got the others to receive, I just let the receive go as it was, thinking that's about all I could get out of those older radios.

Well, I stumbled across some info on the pre-dx mods to improve/increase receive. The info is referring to what they call the D9 mod. I tried this on this stubborn old SSB Echo and found it actually works, but I'm curious if this should be switched (none of my nearby stations seem to be overloading the front end) or if it's safe to just run it like this.

The radio has been completely recapped, two oscillators replaced and a complete alignment, along with the typical cleaning for this old radio.

Is the D9 the best solution for weak receive on these older radios or is there any other way to do it? I've heard something about using the SSB crystal filter by bypassing another circuit, but it was for the 696 boards.

Any info is greatly appreciated. Thank you guys/gals.

 

[nomadradio]

Beats me. In a Saturn, D9 is a 1N4148 that serves to add a capacitor to the AGC circuit, to smooth out sideband-receive audio by making the AGC 'hang' and fade out slowly.

Just what mod is this?

73

 

[Hawkeye351]

It's called the D9 mod is all I know. It seemed to work on this old SSB Echo.

Remove banded end of D9.
Solder one lead of a 1.5k ohm resistor into the now empty D9 hole.
Solder the other lead of above resistor to the free lead of D9.

 

[Hawkeye351]

Got the info from an article by FireBreather over at RadioMods.Co.

Copy and paste:

"

"Super Ears" Modification - D9


HereÕs one that many folks ask me about and I was hesitant to include it here. This modification significantly lowers the effectiveness of diode D9 and greatly increases the injected received signal to the radio. This was very popular when the Galaxy 10-meter radios first hit the market (D7 on the Galaxy DX-series EPT3600 chassis). The modification requires that you remove the banded end of diode D9 and add a 1/4W, 1.5K resistor in-line with the banded end and the now vacated board location. This actually works very well for any distant station giving you an S-1 to an S-5 signal. A typical example is a station giving you an S-3 will increase to an S-9 (relative) without any increase in background noise (as is the case with most preamps). The downside is that anyone in your immediate vicinity keying up will tremendously overdrive the front end of your radio, possible causing damage to the receive portion of the board. Because of this, I ALWAYS perform this modification with a SPDT sub-miniature or micro-mini switch so that the modification can be turned ON and OFF as needed.

DISCLAIMER: Although this modification works great, I can not stress enough the care that must be taken when using it. Careless use of this modification can lead to radio damage. Engage this circuit modification only when copying distant stations. I take no responsibility for any damage incurred as a result of this modification.

Having said that, go ahead and experiment with this carefully. You will be surprised at the results.".

Although it states D7 on the 3600 boards, D9 seems to work fine also on the SSB Echo. Unless I'm confused by an "Expected Perception" of an improvement.

 

[AudioShockwav]

FireBreather

There is a name from the distant past, I remember Chris from his involvement in the CB Tricks/Panther Forums many years ago and I also remember this mod,sans his warning about needing the switch to avoid overloading, never tried it.
Long time ago

73
Jeff

 

[Hawkeye351]

Well, decided to switch it over to the D7 instead of D9 (since it's a 3600 board) and wow what a difference. It didn't bring the noise floor up but it sure did bring the signals up a lot. I just detuned the receive a little to compensate for the dramatic increase. Now the receive seems right.

 

[999]

Well, decided to switch it over to the D7 instead of D9 (since it's a 3600 board) and wow what a difference. It didn't bring the noise floor up but it sure did bring the signals up a lot. I just detuned the receive a little to compensate for the dramatic increase. Now the receive seems right.

This sounds like what I need to do to my old Pluto.