I have a question do I Connect the rf output of my signal generator to antenna output on the 148 gtl ?
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Alignment procedure
- Thread starter kaos513
- Start date
I run the output of the sig gen into a tee fitting and have a 50 ohm dummy load on one side of the tee, and the other side of the tee goes to the radio antenna plug.
Never - and I mean never - key the radio if you have the sig gen hooked up to the radio. Unless you want to fry you sig gen.
Never - and I mean never - key the radio if you have the sig gen hooked up to the radio. Unless you want to fry you sig gen.
My thoughts about the RX alignment were after the fact...that actually makes sense, and I hadn’t thought of it initially.
But as for TX...I have no idea?
TX? You need the AF-Generator (It's still a signal but RF versus AF - Audio side) side to INPUT in to the Audio - Mic side.
Hence the need for a AF generator - or "Two tone"
@kaos513 - are you using your new (to you) generator on this?
Back to @Robb - and I 2nd it, - anyone using RF generator - remember to disconnect the Bias Lines to your Driver and Final if possible - Mirror board or jumper - Many Galaxy and RCI's no longer use these techniques - you will blow up the Generator - so even though the Dummy load SHOULD be there and YOU may have remember to disconnect the lines - it still poses a Hazard to the Radio and Generator alike if you try to key up for a "Quik-look at the scopes output - POOF in one part of the line or the entire chain...
Hence the need for a AF generator - or "Two tone"
@kaos513 - are you using your new (to you) generator on this?
Back to @Robb - and I 2nd it, - anyone using RF generator - remember to disconnect the Bias Lines to your Driver and Final if possible - Mirror board or jumper - Many Galaxy and RCI's no longer use these techniques - you will blow up the Generator - so even though the Dummy load SHOULD be there and YOU may have remember to disconnect the lines - it still poses a Hazard to the Radio and Generator alike if you try to key up for a "Quik-look at the scopes output - POOF in one part of the line or the entire chain...
Those block diagrams are obviously WRONG if they advise to use it for TXing.
Where is the common sense in that?
Please explain.
Using a sig gen is used ONLY for RX alignment.
For testing TX, you use a coax with an indirect RF pickup for the scope and freq counter and out to a watt meter and then directly into a 100w/50 ohm dummy load.
Q: you still haven't figured that all out yet?
Did you burn up your last sig gen before you figured this out?
? ? ?
Im aligning a 148 gtl China made
Attachments
Had to convert 1800uV comes out to 1.8 millivolts as my generator doesn't go up that high in microvolts
If you're adjusting for Squelch, don't use the RF generator to make a signal for that, it's 1800uV is for signals that are 20 over S9 - you do not need to use the RF generator for that.
The Squelch pot, VR3 can be set to Mid-point and left alone once you have all your ducks in a row when your tuning is done.
NB- off
ANL - Off
RFGain - Open all the way full gain
SQUELCH - Fully Counter Clockwise - to OFF
Just remember that you're working with a Radio that has a good effective AGC control - so you will have to exceed the uV limits of your RF generator - DON"T - at least you don't need to - save the trouble and continue to tune using the steps - then go back and tweak VR3...
1,800 uV is like someone parked in front of your house or under your antenna - and you're trying to SQUELCH them out - Remember that AGC is working in the radio AGAINST the Input Gain the Receiver has, so if you can't squelch them out - you already know that with this much signal arriving into your radio - it can do some damage - so why force the Signal Generator to do this step for you?
Here's what I do...it just simpler and easier less hassle because your taking and testing the radio for OEM specs - unless you;ve done a receiver mod, then OEM specs is what you tune and strive for...
Defeating AGC is not for the feint of heart, even Cobra doesn't provide the steps for it - it's not necessary.
If you do this, you are accepting the risks of potential damages to PIN diodes RF front end and FET's used to mix for IF signal processing - DISABLE TX MODE and prevent the Driver and Final from having power to key up - meaning you pull their Bias feeds - before you begin.
Disabling the AGC is not recommended - if you do - you are on your own.
Back to the 148's RX side...
When it's (VR3) at Mid-point , your ok, when it's not, remember to check the level of rotation VR3 needed - to just engage the Squelch when the Squelch control is off it's bottom stop - and ready to engage - you should be able to quiet the receivers own internal noise by just setting VR 3 to mid point, you don't need any more level control than that.
IF VR 3 quiets too soon, you may have missed a coil or over peaked the wrong coils in the wrong mode - reset and retune to rebalance the "hiss" level as well as VR3's action. You have a TOO QUIET Receiver.
IF VR3 needs more turn beyond mid-point before it quiets - then you may have over peaked - you have a noisy receiver and if can be from IF carrier onto unbalanced Bandwidth - tuned too close to Channel 1 or Channel 40.
The Squelch pot, VR3 can be set to Mid-point and left alone once you have all your ducks in a row when your tuning is done.
ANL - Off
RFGain - Open all the way full gain
SQUELCH - Fully Counter Clockwise - to OFF
Just remember that you're working with a Radio that has a good effective AGC control - so you will have to exceed the uV limits of your RF generator - DON"T - at least you don't need to - save the trouble and continue to tune using the steps - then go back and tweak VR3...
1,800 uV is like someone parked in front of your house or under your antenna - and you're trying to SQUELCH them out - Remember that AGC is working in the radio AGAINST the Input Gain the Receiver has, so if you can't squelch them out - you already know that with this much signal arriving into your radio - it can do some damage - so why force the Signal Generator to do this step for you?
Here's what I do...it just simpler and easier less hassle because your taking and testing the radio for OEM specs - unless you;ve done a receiver mod, then OEM specs is what you tune and strive for...
- I do it this way, VR3 to minimum, Squelch control to minimum - as in you hear static hiss...
- Turn Squelch control to 1/4 - up from Minimum position - then turn VR3 until Static stops - you've engaged the Squelch control - note "o'clock" setting of the VR3 pot, is it near Noon? Then you're set.
- Else observe the Rotation of VR3 to open Squelch then close it
- - if you find yourself having SQUELCH ENGAGE turn-on BEFORE you reach noon (like say, 9 - or - 10 o'clock position - then something in the RX strip isn't quite right - you may have inadvertently tuned the RX strip for IF carrier - not your AM / SSB signals - so you may have over peaked a section of the Receive, which then affects the later stages PAST the section - recheck settings - retrace your steps and retune.- your Receiver is TOO quiet...
- IF you are finding VR3 has to be turned PAST noon, to say - 3 o'clock position - then the "L12" thru "L15" you need to check LINEARITY of SSB to AM - that may require you to look and observe the S/RF meter for activity in your re-tune session. You may have over peaked SSB to offset AM or vice a versa.
- VR3 being set to Mid-point is pretty much what Cobra wants to see
- - so if you see Squelch engaging sooner than Mid-point - the Receiver is TOO quiet - retune...
- - IF you see SQUELCH engaging LATER - PAST mid point - The Receiver is TOO noisy - potential Birdie or overpeaked IF section
- Remember that RX is finicky -Channel 1 and Channel 40 - tune for best level balance - then recheck on Channel 20
Defeating AGC is not for the feint of heart, even Cobra doesn't provide the steps for it - it's not necessary.
If you do this, you are accepting the risks of potential damages to PIN diodes RF front end and FET's used to mix for IF signal processing - DISABLE TX MODE and prevent the Driver and Final from having power to key up - meaning you pull their Bias feeds - before you begin.
Disabling the AGC is not recommended - if you do - you are on your own.
Back to the 148's RX side...
When it's (VR3) at Mid-point , your ok, when it's not, remember to check the level of rotation VR3 needed - to just engage the Squelch when the Squelch control is off it's bottom stop - and ready to engage - you should be able to quiet the receivers own internal noise by just setting VR 3 to mid point, you don't need any more level control than that.
IF VR 3 quiets too soon, you may have missed a coil or over peaked the wrong coils in the wrong mode - reset and retune to rebalance the "hiss" level as well as VR3's action. You have a TOO QUIET Receiver.
IF VR3 needs more turn beyond mid-point before it quiets - then you may have over peaked - you have a noisy receiver and if can be from IF carrier onto unbalanced Bandwidth - tuned too close to Channel 1 or Channel 40.
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