Mirage pre-amp question

[WE...@aol.com]

I have a 160 watt brown faced Mirage 2M amplifier (B3016).  The amp works as expected for the MJF that it is...not real linear, but as well can be expected, if driven with a modest amount of power.

My question is about the built-in pre-amp.  It does not raise the noise floor in my receiver when switched on. 

I think it should be noticeable when it is switched in and out.  I hear the relay click, but there is not indication that the pre-amp is doing anything.  Received signals come through the same whether it is switched in or out.

  Am I wrong in thinking I should be able to hear some difference, with it ON or OFF?

 I have other Mirage amps, with the pre-amp function, and they definitely do make a small difference in the received signal, even if it does not help the S/N ratio.

  I know these pre-amps do not have a low noise figure, so I don't expect it to be of much, but I would think I should be able to hear some difference.

 Thanks,

  Rod J 

[Jerry]

GE Rod.. No, you should see a definite jump in S Meter readings.. ie; S3 then switch on the pre-amp..S-6 or 7.. so I would say the pre-amp part is 'not working' ! I run a few MFJ Amps..my 1015G on 6M, the pre amp is starting to get weak..ie: only raises the incoming signal an S unit or so.. my B-2530 300W on 2M..S2 noise w/out..S7 with it on !  Probably an easy fix..or you can always go with a mast mounted one (better anyway than the 'brick one') but you would need a Sequencer to protect it ! Would probably be 'cheaper' fixing the MFJ though ! If your not a fix it ur-self kinda guy, I am sure there are 'many in the PNW' that have the know how to di it !  73 and Good Luck !
Jerry
VE6CPP
DN39or 

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[Jerry]

Sorry.. CW.. I meant 'Do It' ! ;o)

On 5/17/2014 12:17 AM, Jerry wrote:
> di it ?

[Edward R Cole]

Rod it should produce a rise in background noise and maybe raise the s-meter a little.  I would say your preamp is not turning on.  Have you looked inside to see if the wiring to the switch is intact?  If the preamp transistor were shot it should make receive worse when turned on. I assume an antenna is connected.  With no antenna there might not be much noise increase.

I would assume the Mirage preamp NF is about 1.5-2.5 dB and gain about 10-dB.

73, Ed - KL7UW

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73, Ed - KL7UW
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[Loren Moline WA7SKT]

Rod,

I would guess that if the preamp is actually switching in and it is bad that it would knock the received signal down when it was powered on. I am guessing it is not actually even switching.

Loren Moline  WA7SKT

Member: Pacific Northwest VHF Society and ARRL
Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
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From: pnw...@googlegroups.com
Date: Sat, 17 May 2014 02:04:59 -0400
Subject: [PNWVHFS] Mirage pre-amp question
To: PNW...@googlegroups.com

[Edward R Cole]

I agree with Loren on this.  A bad preamp usually makes reception very poor or impossible.  Could be simply a bad switching transistor or relay.  Visual inspection may even show the problem or simple tracing dc voltages from the preamp switch backward.  Might even find there is no power to the preamp switch which would be a simple fix.

73, Ed - KL7UW

73, Ed - KL7UW

[Loren Moline WA7SKT]

Rod et al,

I have a Mirage 1016 in which the preamp does not work. It does not switch in RLY2 when the preamp switch is turned on but the LED comes on. SW2 I believe it is has 2 sections. One turns on LED and the other is the preamp .

When we get a bad weather day I may dig into it and look for the problem. If the schematic I have is accurate I am sure I can find the fault. It could be a common problem with these beasts.

Loren Moline  WA7SKT

Member: Pacific Northwest VHF Society and ARRL
Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
Starchat IRC: Channel = #hearsat
RF Electronics: Starchat IRC: Channel = #rfelectronics
Grid: CN86bx

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From: lmo...@hotmail.com
To: pnw...@googlegroups.com
Subject: RE: [PNWVHFS] Mirage pre-amp question
Date: Sat, 17 May 2014 07:41:11 -0700

[Loren Moline WA7SKT]

Well I know why the preamp in my B1016 does not work, The preamp board and relays were taken out of it by a previous owner. I'm not really worried about not having it.

I found out I only get about 140 watts out of the amp and also this is because the IC-706 only puts out 7 1/2 to 8 watts.

Anyone know if there is an adjustment in the IC-706 besides the menu where you set the power level.

Looks like all bands have reduced power so I think it is related to a pot in the ALC circuit which sets max power when it is set to high in the menu.

I guess I could look at the schematic.

Loren Moline  WA7SKT

Member: Pacific Northwest VHF Society and ARRL
Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
Starchat IRC: Channel = #hearsat
RF Electronics: Starchat IRC: Channel = #rfelectronics
Grid: CN86bx

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From: lmo...@hotmail.com
To: pnw...@googlegroups.com
Subject: RE: [PNWVHFS] Mirage pre-amp question

Date: Sat, 17 May 2014 09:16:42 -0700