I just love typos  Sorry

http://home.comcast.net/~msed01/decometer.html

is the proper web reference.

Well, I'm a little surprised I've not heard any reply to this inquiry.
In the meantime I've essentially answered my own question and published my findings. If anyone else is curious about how an RF Phase meter functions, or is used, you are welcome to visit http://home.comcast.net/~msed01/decometer.
73 to all and happy tinkering.
KA2QFX

I’m pretty stumped on this one.  I haven’t been able to find any references or literature on this.
I have a DECO Electronics RP-100 Reflectometer/Phase Meter RF line sampler.  Looks to be about 1960s vintage.  Apparently never used, or at least, never had any wiring soldered to it’s terminals.
It has four terminals and a common connection for remote meters and I’d like to build a meter panel for it.
I need to know how the PHASE METER(s) are supposed to be set up.  
Here’s what I know so far.
The POWER FORWARD and REFLECTED are straight forward as you might expect. Two capacitively coupled line voltages are summed with in-phase and out-of-phase derived voltages from a common magnetically coupled line current winding (40 turn air core toroidal). The circuit is almost right out of the “Handbook”.  It drives two 100uA meters just fine to about 1000W without any padding.  
They are connected to terminals Common, 3, and 4.

Now here’s where I have a problem.
Terminals 1 and 2 are obviously the phase metering terminals.  These voltages are derived as follows:  The same line voltages sampled for the power metering are further divided (capacitively) and connected in SERIES with smaller (10 turns), separate, current sampling loops and then rectified.  The other difference is that the diodes are reversed for one, so the output derived using the FORWARD power voltage sample is negative, and that using the REFLECTED power voltage sample is positive.

Looking at these outputs with matched, shorted, open and various reactive loads yields no clue as to how they should be metered.  They always generate voltages but not in any pattern that seems to follow what antenna currents do.  Does this require two meters? One differential meter? Zero center, +/- 180?  Anybody have any ideas?

Thanks for your insights.

Mark
KA2QFX

Your post doesn't answer a lot of questions that come to mind regarding your problem. First, having changed the finals have you carefully followed the procedure to nuetralize the new finals.  "New tubes",especially todays overseas stuff, can have wildy varying interelectrode (grid to plate) capacitiance ratings. For instance, 6146B are generally NOT interchangable with 6146 in RF applications for this reason. Either way, you need to neutralize whenever you make any changes to your finals, even swapping their positions.

Aside from that, you SHOULD see a pronounced plate current dip (Ip) that corresponds to your output PEAK.
Starting with a minimum load (fully counter clockwise) this dip should be very deep, or sharp, and correspond exactly to your max output. As you increase the load (clockwise) this tuning would get broader and less deep until it reaches a 200Ma minimum. Assuming you've maintained adequate drive (some ALC reading) througout the tune-up.

Remember also, most neutralizing caps have plate voltage on them and MUST BE ADJUSTED WITH NON-CONDUCTIVE TOOLS!

If this dip does not correpsond to your peak output, regardless of load setting, you are likely in need if neutralization.  The 520 has a nice way to accomplish this using the Screen Grid cutoff switch on the back of the radio.  This allows minimizing the grid to plate leakage using another receiver, or an RF voltmeter on the output, and adjusting for minimum signal, without developing any plate current.

 Another method I have used to confirm optimum nuetralization of radios (without this Screen Grid switch feature) is as follows:
Set LOADing at a minimum, and preferably using a (non-reactive) dummy load, apply sufficient drive to obtain a plate current reading, staying well below full load Ip levels.
Adjust plate tuning through (dip) resonance and note rise in plate current on either side of the dip. A well neutralized stage will usually exhibit a symmetrical rise in plate current above and below resonance. If not adjust neuralizing cap accordingly until rise is equal.

Assuming nothing else is wrong, this should either resolve your problem or identify that something else has indeed failed.

One last thing, if you do find you have a problem with cathode resistors, these must be replaced with non-reactive carbon type resistors. Metal film, wire wound, etc, will NOT work!

Best 73,
Mark

Never mind. I found the answer, and some other info. Turns out this is a much maligned radio. The analog is pretty OK but the digital parts are very primitive. Being among the first systhesized, PLL/VCO radios ever produced it makes one appreciative of today's technology. Mine works great though, in spite of sluggish and somewhat noisy VCO.
73

I've just repaired my IC-245 (an oldie and not a goody) for all mode operation after years of dedicated simplex use on packet.  Now that eveything works, can anyone tell me how the duplex split is programmed?

Thanks in advance.

Mark

Hello Joe,

        The mike you have is an SBE Model 100X. It's a great mic, I use mine on 2 meter FM these days
but it's seen plenty of service.  I don't have a schematic of the amp but can probably help you out if you're just trying to rewire it. If the amp is fried I'll have to reverse engineer mine a bit. I've done that for my
D-104 (TUG-9), Turners, etcetera but not the SBE, 'cause that's the only mic that's never died on me or
given me RF problems.
      Let me know what your problem is and I'll try to provide you with what you need to know.

Later,

Mark KA2QFX
msedutto@mindspring.com

Boy, that brings back memories of when I used to spend too many hours on local VHF 'machines'.
Some people's mic habits, as well as differences in radios can make for quite the variety of audio in the shack.

What you want is something that is seen on many 'vintage' recievers known as AVC, Auto Volume Control.


You should be able to adapt the one of the many older speech compressor designs using and Op-Amp to  drive your ext speaker after the radio.  The AVC works in the feedback circuit to vary the gain of the amp (inverting), or reduce the input to the amp (non-inverting), using an FET or bi-polar trasistor respectively.  The transistor is driven by a portion of the amp's output which is diode rectified and filtered with a cap and resistor to produce a slowly decaying control voltage.  A sudden signal peak charges the cap quickly and reduces the circuit's gain and keeps it reduced as long as the 'loudmouth' keeps charging it.  Once he unkeys the filter discharges and the gain returns to maximum.  

If you make the filter's time constant short enough you have a sort of 'speech compressor', as long as you drive it hard enough to activate this feedback circuit it will limit the high peaks and amplify the lows.  Slow the filter way down and it sets a limit for max output.  

I know there's a circuit for such a simple design in the ARRL handbook from yesteryear. You'll have to scale the output up a bit to drive 8 ohms.  I wouldn't try messing around with anything in your reciever though.

I have often wished I could send attachments on this board. I'd send you a simple sketch. I suppose we eat up enough disk space now.  

Hope this helps.

Mark

This is a repeat of an earlier posting to a similar question.  With some edits.
I strongly feel that ALC feedback from the amp is a valuable safeguard against overdriving the amp on voice peaks or an accidental condition.  Most common cathode amps generate ALC by rectifying the RF drive, and many provide an adjustable output. If you want to minimize the ALC for maximum output from the amp you can, but don't turn it down so low that it's ineffective.  

It is true that RF drive derived ALC does not take into account different gain responses of some amps on different bands, but that's a design compromise that amp manufacturers poorly decide upon. A better, and far more costly, ALC circuit would monitor grid current at a fixed limit, but that's rare except on grid driven amps.

As far as ALC compatibility goes this is not a concern. My amp can generate up to -72 volts of ALC, I've never seen a problem with any of my exciters, mainly because the ALC never goes below  where the ALC shuts down the exciter, about -5 to -7 volts.  The impedances involved in ALC circuits are so high they are not likely to permit sufficient current flow to cause any damage should it max out. Besides, excessive ALC could only be generated if the ALC circuit in the radio isn't controlling the output. So excessive ALC from the amp would be a secondary result of a MUCH bigger problem anyway.

I use a grid driven (Class AB2) tetrode amp. Without ALC I would rapidly consume my paycheck in tubes. The much tougher cathode driven circuits are no excuse for letting your peaks overdrive your amp or running an open loop system when alternatives are provided.

One additional benefit of using ALC with an amp is additional compression. The gain of the amp will permit low level signals to be amplified linearly while compressing higher drive levels down to safe levels. Simply turning down your drive to prevent peaks from overdriving reduces everything. Most processors use the ALC action as part of the processor's gain loop. Turning down the drive below where the ALC functions and you lose that processing function as well, futrther limiting the potential of your station when using the amp.

I therefore strongly reccomend using ALC to MAXIMIZE the potential of your amp and exciter as linked components and prevent occasional undesirable products as well as possible catastrophes.

Mark
KA2QFX


 Regarding the mention of the ALC causing RF feedback... it is more likely that the ALC line is picking up stray RF and rectifying it. This would cause the transmitter to be effectively AM modulated at a very low frequency.  A few wel placed ferrite beads on the ALC line would likely clear that up. Or better yet, find out where the RF is coming from and cure it.    

John:
        Sorry to hear your still doing battle with this problem.  I can't find a copy of the email I sent you regarding putting this rig back together. I was going to review it to see what I may have left out that could help you. Want to send me a copy if you still have it and I'll go over the details again if you like.
     You didn't mention if you ever got the VOX board back in. If so, chances are you've discovered why you took it out in the first place.  Certaily the VOX board was overloading the 12 volt supply if it wasn't in the radio.
     Actually,  I have to agree with the last post. If you weren't able to restore the radio by reconnecting the VOX board with all the detail I gave you perhaps someone needs to troubleshoot it down to the component level, or at least troubleshoot the 12 volt overload board by board.  Could be anything since 12 volts appears on almost every board, and if you're not familiar with following schematics you're best advised to ship it off somewhere.
    Hope you get things resolved, it's a nice radio.

73,

Mark
KA2QFX

The law is very interesting in this regard.

My reading and understanding of FCC regulations (Parts 95 and 97) is that it is not illegal to sell an otherwise legal amplifier to a non-ham. It is however illegal to commerically manufacture such amplifier equipment for sale without type acceptance from the FCC.  It is also illegal for anyone in the Class D radio service (formerly licensed CB operation now unlicensed) to possess any amplifier capable of amplifying signals in that band.  Part 95 specifically states that "posession within the premises" is sufficient grounds for prosecution even though no evidence exists to indicate that it was ever used to amplify signals from an 11 meter station.  

So my guess is you would not be committing any crime (legally) by selling it to a non-ham.  He would be committing a crime by receiving the amplifier only if he had an 11 meter station.  Strange isn't it?

Nevertheless, I wouldn't sell any amps to a non-ham. Sadly I've seen plenty of flea market dealer (hams) that sell dirty little class AB, unfiltered,  solid state units to the CBer's by the boatload that crank out 200-300 watts.   You are certainly under no obligation to sell to this bidder, and eBay will back you up on that from several disputes I have heard of.

In short, yes, you should disconnect because you never know what might come your way.  Normally when not operating I left my coax switches in the grounded positions to protect from minor static and preciptation induced charges, etc. If I knew a storm was coming or leaving on an extended trip I'd disconnect most everything.

I have two fairly long and thorough docs on my web site regarding grounding and lightning if you care to read them.
http://www.bridgeport.edu/~msedutto/amateur.html

I must agree I agree with much of the previous posts.   The rice burner radios all seemed to have a unigue sound in their earlier generations. To my ear the ICOM was always the sharper DX type sound with abrupt but clean compression at the higher drive levels. The Kenwood had rather broader or flatter response and compressed sooner giving a more natural sounding envelope. And the Yaesu seemed flat but lacked low end smoothness and got somewhat distorted when ALC levels rose above a relatively low compression level.

Nowadays they all do tend to sound more similar and the digital enhancments to the radios internal adjustments make this more tailorable.  And some people say you have to match the right mic to the right radio. I've always felt it's more a matter of matching the mic to your voice.

One other thing that I've noted about "Kenwood Audio" (which is a noticable characteristic once you know what to listen for) was actually explained to me by a Kenwood tech out in their Ca service center.  He claimed that Kenwood designed their filters to have minimal group delay characteristics in their passband.  This explains a lot about their sound. This is a very notable quality when speaking of FM receivers where 75 KHz of bandwidth at 10.7 MHz must pass. I hadn't thought that 3 KHz at 7 - 9 MHz would be that big a deal. But it appears that at the band edges, where phase shifts become most pronounced, filters don't care what the passband width is, they shift regardless.

The resultant phase errors when recombined in the following stages result in a unigue type of sonic coloration which when pronounced is guite noticable. While this coloration may not be "heard" in the normal sense the psychoacoustic sensitivity of the human ear to phase shifts is well documented.  
This is most easily demonstrated when listening to a recording made at some distance from the audio source. The recording sounds echoey and distant while a person standing at the same location as the microphone does not hear any echo. That's psychoacoutstics at work in the brain.  The problem I have with this is at 8 - 9 MHz even a max phase shift of +/- 90 degrees is only a few microseconds. At audio frequencies I would think any phase errors from such a small delay would be less than detectable. But maybe not, or maybe something else is being introduced and transposed to the audio. I don't know but wouldn't mind hearing from a more knowledgable source. Any Audio Engineering Society  geeks out there??

He also claimed that Kenwood's same design goals gave the passband less ripple. Since crystal filters are simply multiple filters with different centers overlapping there are actually band edge effects throughout the passband. How they do this he didn't tell me. But Kenwood's filter skirts do tend to be a bit less sharp than ICOM's.

Whether this is the reason for the audible difference or not I can't comfirm.  What I do know is I like "Kenwood Audio". For the kind of operating I do I find the ICOM (older one's anyway) audio abrasive and fatiguing after an hour of field day activity. I can listen to the Kenwood all day and then some.  Yaesu's haven't been a problem for me, but I still like the Kenwood better. But I'm not a DX hound either.

Everybody's got the best bird dog I guess. In the lexicon of today's educational system "There are no wrong answers"  Yeah, right.

And I agree that oxygen free copper, ultra low capacitance, litz wire speaker cables are not verifiable in my living room either. But I do seperate the bass from the midrange/highs over two sets of fairly heavy cables and that did make an audible difference.

73,

Mark
KA2QFX
 

Oh, I forgot to mention, as previously posted, you do need a good connection to the chassis. You didn't say if your hitch was frame or bumper mounted. The latter are frequently insulated from the chassis if you have 5 mph bumpers commonly found on most cars these days.

I made a bracket which bolts directly to the frame of my Jeep Cherokee just inside the bumpers. It's not only an excellent ground. But the bumper affords it some protection from off road hazards.

A VERY well grounded mount is esential. If you have to use a ground strap make sure it's nice and wide and the connections are clean and then greased upon assembly to prevent corrosion.  A 1 or 2" wide strip of copper roof flashing works very well.

Short  mobile antennas are rarely 50 ohms. On ten maybe a 1/4 wave whip will be pretty close but as the antennas get shorter their radiation resistance drops. On 75 meters my 13' center loaded antenna, at resonance, has a resistive value of only about 10-15 ohms. Naturally, if you're not dead resonant, you'll have some reactance in their as well.

My solution for the  lower freguencies, where the antenna is significantly less than a 1/4 wave, is to use an unbalanced to unbalanaced tranmission line transformer. It's virtually frequency insensitive throughout it's VERY broad passband and extremely efficient.  My 4:1 UN-UN brings my 10-15 ohm 80m antenna up to 40 - 60 ohms and I can run without the inboard tuner at it's resonant frequency. Where it's off resonance (+/- 10 KC) I use the tuner and the transformer still provides a much more efficient match to the 50 ohm cable.

You may want to consider building something like this. BTW, my signal reports @ 100 watts is generally right up there with the fixed stations. Hearing is believing.

I have a web page detailing my mobile antenna setup describing the transformer if you care to read up on it at http://www.bridgeport.edu/~msedutto  Details of the transformer feed arrangment are on the last page of the construction article you'll find there.

Good luck.

Mark KA2QFX