949 Receive w/ Pre amp issue

[JCH]

I have a 949 and Tx Star 350, when I engage the pre amp on SSB, upper or lower, it actually reduces the receive by an S unit or so, and distorts the recieve with a rough static. It does this only on SSB, and it seems to work as it should on AM. The 949's SSB receive is great w/o pre amp.

Also, the pre amp works as it should on AM and SSB on another radio I have. This issue popped up out of the blue with my 949. Do you guys have any input or ideas on what might have gone wrong? Any help is greatly appreciated.

 

[Robb]

Sure, either turn down the RF gain on the radio or turn off the receive boost on the amp.

 

[9C1Driver]

In most cases the pre-amp feature on an amplifier is worthless. On a rare instance late at night on a quiet channel they can help, most of the time all they do is boost incomming noise. I would just leave it off.

 

[JCH]

Thanks. I understand what yall are saying, but it's not the regular signal boost static, something's wrong somewhere. Difficult for a layman to explain.

Could a bad diode/other part in the radio's receiver cause it, maybe?

 

[QROdx]

best way to explain it is that the 949 has a hot receive and the preamp is overloading it.

Like Robb said.....

Sure, either turn down the RF gain on the radio or turn off the receive boost on the amp.

 

[JCH]

Thanks for the info guys - I appreciate it.

 

[Robb]

The following is an excerpt from the Defpom page. If this mod had been done to your 949 before you got it; then this may be the reason that this radio has an over-loaded receive when the amp's receive amp is turned on. Check the part location in you radio and compare and see if it has been modified as such.

". . . Super Ears" Modification - D9

Here's 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 10-meter 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. The Galaxy DX959 and 949 front panels are heavily populated so your installation options are limited. I installed my switch between the Clarifier and Talkback controls.

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 . . ."

http://www.radiomods.co.nz/galaxy949_959ept069610z.html

 

[JCH]

Thanks Robb, I'll check that and keep poking on the radio and try to figure it out. What's puzzling is that it worked fine before and out of the blue it started acting up. The fun part's getting it set up right, once that's done it's time to start over.

 

[psycho]

In most cases the pre-amp feature on an amplifier is worthless. On a rare instance late at night on a quiet channel they can help, most of the time all they do is boost incomming noise. I would just leave it off.

The preamps in the Texas Stars are way too powerful and just pickup way too much extra noise. Turn it off, problem solved. PM me and I'll give you my paypal email address so you can send me my $30 diagnostic fee. :laugh:

 

[JCH]

The preamps in the Texas Stars are way too powerful and just pickup way too much extra noise. Turn it off, problem solved. PM me and I'll give you my paypal email address so you can send me my $30 diagnostic fee. :laugh:

Will "thank you" suffice? You sound like these CB shop dudes along I-20 down here.

 

[JCH]

Replacing the mag mounted Wilson 1000 with hard mounted 102" whip fixed the preamp issue I was having.<More audio>