One little piece of "alignment philosophy"......

[guitar_199]

This one is just one of my radios that I am studying.... as such I do not have it on the bench. I am hoping that this question will just be "philosophy"..... more to the point....... "what am I missing here"!!!!

The patient is a Royce 1-600. The photo clips are from the SAMS CB Photofact for it.
I will continue below the pics.

(alignment instructions)

(driver and final circuit)

(output filter circuit)

------
OK....here we go.

The last step of the transmit alignment discusses "removing the jumper at TP and inserting a
0 -1A milliammeter in the circuit. That sounds confusing.... as "0 - 1A" suggests one thing....."milliammeter" suggests another. But ride with me a minute......

The final circuit snippet shows where the jumper is..... in the collector circuit for the final... right where I would expect it to be.

The output filter snippet shows where L17 is..... right smack in the middle of the filter.

Here comes the question..........

The instructions say...... Adjust (L17) for 5 watts maximum.

Okay, I know the instructions (at the top) say to connect an RF watt meter.......but two steps earlier has you adjusting the final for 3 watts. So we are at three watts.......

Now....this step has me adjust L17 for 5 watts.

The question is..... "why did they have me put in a milliammeter when they never give me a current setting to shoot for"? Nowhere in the document do they say anything about what "current" I should adjust for.....rather....they are just telling me to spin L17 until I get 5 watts.

Am I misunderstanding what I am supposed to be doing? Is the "5 watts" supposed to be calculated by "collector voltage times current"? Or am I really setting the RF out of the radio at 5 watts?

Since they refer to this as "setting the final input power" it seems to make a little sense that I should be measuring the collector voltage times the current that I read on the mA meter and adjusting L17 for that... but they don't make it clear.

Anybody have an opinion on this one?

Thanks in advance!

 

[Robb]

Makes me wonder what these engineers were smoking at the time they wrote it up . . .

 

[DoctorAudio]

I think what they are referring to is the 5 watt "input power" limit on 11 meter.
You would use the formula: P=VI Or in this case P divided by V
So V is 14 volts and the watts you are shooting for is 5 watts.
5 divided by 14 = 0.3571428571428571 amps.
So you dead key the radio and adjust L17 until you are drawing .36 amps of collector current. (360ma)

 

[Justme]

Should be more,
Losses in the PI circuit, transistor efficiency is at best 70% so i would guess more at 0.5 Amp
Since the value is not given it's guess work.

 

[Handy Andy]

There are Ammeters that read 1A full scale - so this manual was posted, printed, published in that era of the older analog scale logarithmic meters.

Otherwise, It would have claimed to use 0-1mA - but it wants you to use a 1 Amp rated - Full Scale Deflection - so at 1 amp you have 100% full scale.

Examples, as a serving suggestion...
​

If you remember the DVM - you have a 1/4 to 1/25th Amp rated fuse for the Amp scale and protection - so it uses shunts - this allows that SURGE to pass thru the shunt.

But if the measurement is done in error in wrong scale (like those RWOB Mods you didn't expect to see) and even you have used PROPER Scale on the meter, the Fuse will still pop because of the inrush current along the shunt and it's detector - killing the display. But! The DVM lives to see another day - just fix the fuse.

IF you have a DVM from those older days, that can use the 2A or 1A scale - that is what they recommend.

But the Gratiicule, (Gradients) Reticule Scale, those tiny little tick marks - they should be / are in mA so your Analog days of yore have some means of accuracy.

For DVM, it is your Decimal...watch your multiplier below that decimal mark.


The rest of it?

Remember my graphic from earlier - it (Cobra 29) asks you to tune L11 for the largest dip in power, then retune the output coils of Driver and Final stages - to couple into it - to maximize it, but then detune the L14 slug to meet 4 watts.

Look for "step 4" in Step 2 Transmitter alignment...

​

The process is to get your 3 watts, - tune for max, then RESET carrier power to meet the 5 watts.

The initialization - being the pre-set to 3 watts - is similar to the "Detune" on the L21 and L17 of a Cobra 29.

You bottom out slugs to force the radio to make power into detuned circuits, but they still will show 27 MHZ band pass - so the 3 watts you're working with - is the Pre-set - then tune, peak, then reset to proper output wattage.

I'm posting this as I get interrupted for "dinner" ...so work with me here...

Your last graphic has the answer you need.

​

It's L18 the 52 MHz filter - since these are a little more cruder -3dB down type of slope filters, L18 and POINT12 is the hangup - that you have to peak for RESONANCE of your 2nd even order harmonic - then peak out the L17 and all others to maximize their transfer.

• When you ""peak for Resonance" on L18, look at the circuit at Point 12, it is a SERIES circuit, so it's a SHUNT across the line - so you tune it to remove the 52MHz (2nd harmonic)
  • That's your Peak - the dip - it is tuning out ~52MHz your 2nd order.
• So when I say "Peak" it means to obtain the greatest amount of power REDUCTION (DIP) across this SERIES circuit - means it will shunt away some power to ground - that being mostly in the 2nd harmonic. So you'll see a "Dip" not a "peak" - but a LOSS of power thru this set of parts. It's taking away your harmonics.

If you have a spectrum analyzer, work this L18 coil while you watch for the RF power Dip - you'll see what that little Series circuit does.

To answer your meter question...

Measure your voltage at the Tap point - where you are placing the mA meter.

Then measure your amps, this being in mA...

Watts = Volts X Amps

So if it's 12 Volts DC...

mA is 1/1000 (oh, geez!) of an amp - so your scale would be - mA While measured for 1 A (Your Full scale) is 1,000mA would be 12 Watts...- you want 1/3rd of that, or about 333mA.~ Shoot for 350mA. Which then gives you your 4~5 watts

 

[DoctorAudio]

The scan of the SAMS the OP posted states 14 volts, not 12.

 

[guitar_199]

Thank you gentlemen....... putting all of this together makes sense. I am definitely copying all of this out to a nice file I can keep but, again, thank you much for the quick response.