Re: SSB 23cm masthead preamp update


Alan G0XBV
 

Well, Mike, you could re-assemble it as is, test it to see if it's working and then as I presume it's a thru device, place it into your proposed setup, switch it in and out of cct and compare the s/n.  Even if you don't have any pro test gear, a weak carrier with an FM detector should give you some idea if there is any improvement from using it and then you could proceed from there if you felt further improvements were likely to be advantageous

Al G0XBV


-----Original Message-----
From: 'mike' mb.golfmad@... [ukmicrowaves]
To: ukmicrowaves
Sent: Thu, 13 Aug 2015 10:10
Subject: Re: [ukmicrowaves] SSB 23cm masthead preamp update

 

Thanks to everyone for their replies, I'm thinking of changing the MGF1302 with a NEC32584C  if anyone has any experience using this device I would appreciate your comments. My logic in changing it is this...my DB6NT has a listed NF of 0.6dB so using the Preamp with 0.8dB, will only degrade the performance. Maybe not really worth making the effort, but as I have it all apart anyway, should I not improve it if I can?... or am I chasing fairies?
 
mike G6TRM
 
 
----- Original Message -----
Sent: Wednesday, August 12, 2015 8:01 PM
Subject: RE: [ukmicrowaves] SSB 23cm masthead preamp update

 
The spec sheet says 1.4dB at 4GHz, it will be lower at 1.3GHz.
 I used one in the G3WDG 23cm Preamp published in Microwave Handbook Volume 3 p14.8 and managed 0.65dB at 1296MHz
Dave
G4FRE
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 12 August 2015 16:50
To: ukmicrowaves@...
Subject: [ukmicrowaves] SSB 23cm masthead preamp update


Further to my attempt to restore my SSB 23cm masthead preamp, I have stripped it down, removed the faulty coaxial relay, and fitted the replacement.I've cleaned up the PCB by removing all the residual flux etc. Close inspection found the active device is a MGF1302. This is interesting as the spec sheet says its for 4-12GHz. it's best NF is 1.4dB.
 The spec of the SSB preamp says it's 0.8dB..
I know that some devices have better gain when run below their design frequency, but does it follow for NF too?
Also  0.8 dB is not that state of the art for 23cms these days, can anyone suggest an alternative to improve the NF that I can fit as a direct replacement, with maybe a tweak of the bias?
regards,
Mike G6TRM



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