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RFX95HD only seeing 50w peak

I've watched that video before. And I concur on the imaginary "0" SWR claims from other cbers.

I've heard a lot of them claim their SWR is 0 or flat, no SWR. I normally laugh when I hear them say that and then proceed to explain to them what I think is correct. Which I always get criticized on.

My theory:
A perfect SWR is not 0, or a 1:0.
First off, a perfect SWR is equal to a 1:1.
1 is not equal to 0, and 0 is not equal to 1, therefore a 1:0 is not a perfect SWR because it's not at unity, the numbers don't equal each other.

A perfect SWR, in my opinion is when the resistance AND reactance both (impedance) are 50 ohms resistive component and 0 ohms reactive component. A 1:1, and match what the radio or swr meter should see. Although we all know swr meters won't show the reactive component (capacitive or inductive), so you never know what the reactance is, because all the swr meter looks for is the resistance of the load, not the reactance. Only an analyzer will show both.

I've also heard so many people claim their IMPEDANCE is 50 ohms, again I laugh because they're confusing the resistance component as the impedance. The impedance isn't just resistance, it's a combination of resistance AND reactance (+-j).

Resistance = resistance
Reactance = capacitance or inductance
Impedance = combination of resistance AND reactance.

Therefore, to have a perfect SWR, the load must equal what the xmitter or analyzer needs to see for maximum performance, which is close to 50 ohms resistance as possible along with a reactance as close to 0 ohms as possible.

Many will argue the above, but we all have our own opinions on SWR theory.

I actually tested this out on my truck one day.
I used a 102" stainless steel whip mounted on the rear passenger bed rail of the truck, and an analyzer.
I connected the analyzer directly into the base of the whip, no jumpers or adapters were used. I then tried 4 different lengths of the same type coax.

At the antenna input, with analyzer directly connected to it the resistance was 49.45ohms and the reactance was around .95ohms, I know, awesome right, lol...
I then hooked a 9ft length of RG8X (VF = .82) to the antenna base, then checked the impedance at the radio end of that coax with the analyzer. The resistance was very close to the original resistance at the antenna, but the reactance was up around 17ohms, although the SWR still showed decent.

I then replaced the 9ft coax with an 18ft length (never did like running coax lengths that are equal to a physical half wavelength) of the same type coax. The results were different and not desirable to me.
The resistance went to around 53 ohms, but the reactance skyrocketed up to around 28 ohms, yuk.. No where near what it is at the antenna.

I then replaced that 18ft coax with a 21ft piece of the same type of coax (heard others say that 21ft is a magic number for 102" whips). The resistance leveled out to 50 ohms, but the reactance dropped to around 12 ohms, still no where near the reactance at the antenna itself.

I then decided to try nulling my coax of the same type by using the velocity factor figure according to a formula I once heard about. My length came out to be 15ft 2.25in. I installed that length, and low & behold the resistance stayed between 49 ohms and 50 ohms (can't rightly remember the exact number) but the reactance showed ALMOST identical to what it was at the antenna. About 1ohm reactance, which was very close to the .95ohm reactance at the antenna.

Been running that length every since, and several others tried it out also on their base setups by replacing all their coax from the antenna run to their jumper runs doing the same identical thing I did. They all improved on xmit signal by 1db to 2db more on everyone and their receive improved by about the same.

I've explained to them that the coax manufacturers don't list the VF just to list it, just so you'll know what it is, for no reason. They list that number for a reason, so you can tune your coax to remove any reactance (capacitance or inductance) that may be present in the coax for a given frequency. I've also explained to them that antenna manufacturers design their antennas for the lowest reactance as possible to improve the performance, therefore you can't just throw any old length of coax onto that antenna because you'll be introducing reactance back to the antenna that was designed to have the least amount of reactance as possible, thereby hindering the performance of the entire system. I've also explained that mixing coax types is a no no, because you're combining differing reactances.

A typical SWR meter is a dumb device, as it doesn't present the reactance present in the system.

The radio expects to see 50ohms resistance with 0ohms reactance, as with the antenna designers objectives in designing their antennas to be as close to 50ohms resistance and as close to 0ohms reactance. Why introduce that reactance (which cancels out performance) to a system that is designed to not want any of that reactance?

These are just my opinions of the theory of SWR, not written in stone, so please don't bash me for my opinions. Like I said, I tested it in real time with an analyzer and on the air tests, along with a few of our locals, and it has proven to work for us.
 
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So, back to the RFX,
Should that VR be adjusted for SWR indication on the radios meter, ma draw or gate voltage?

If for ma draw, how should this be done?
If for gate voltage, what's the best way to set it?

I just adjusted it for lowest swr reading on the radios meter down from a 2 to a 1.1 on the radios meter. Now, everyone says I jumped up in signal and modulation is even louder but still very clean, but the RFX heats up quicker when long winded and gets so hot you almost want to yank your hand off of it.

Originally the indent in the VR faced forward, as they come originally, now it's pointed down toward the speaker cover at about the 5 o'clock position.

And now, when I just key up, with no modulation the meter light goes dim. Before it would dim most when modulating, but now it just dims when keyed up and doesn't dim any more or less when modulated.

It's not my radio, I'm just installing the RFX and testing it out for the owner before he gets it back. I don't want it messing up with him due to me overlooking something or not doing something right.

Still same output of 50w max.

These RFX units are not in my line of knowledge, lol... Others are buying them and asking me to install them since I'm the only radio guy around here. I'll just experiment with my own rfx, but not others.
 
So, back to the RFX,
Should that VR be adjusted for SWR indication on the radios meter, ma draw or gate voltage?

If for ma draw, how should this be done?
If for gate voltage, what's the best way to set it?

I just adjusted it for lowest swr reading on the radios meter down from a 2 to a 1.1 on the radios meter. Now, everyone says I jumped up in signal and modulation is even louder but still very clean, but the RFX heats up quicker when long winded and gets so hot you almost want to yank your hand off of it.

Originally the indent in the VR faced forward, as they come originally, now it's pointed down toward the speaker cover at about the 5 o'clock position.

And now, when I just key up, with no modulation the meter light goes dim. Before it would dim most when modulating, but now it just dims when keyed up and doesn't dim any more or less when modulated.

It's not my radio, I'm just installing the RFX and testing it out for the owner before he gets it back. I don't want it messing up with him due to me overlooking something or not doing something right.

Still same output of 50w max.

These RFX units are not in my line of knowledge, lol... Others are buying them and asking me to install them since I'm the only radio guy around here. I'll just experiment with my own rfx, but not others.
You should turn the VR back down, it is not for the SWR. It is for the bias adjustment. It sets the idle current for the transistor and makes it so it is just about to turn on. This is needed for an SSB rig because in sideband mode the transistor will turn completely off between signal peaks causing a choppy sound. The carrier in AM mode keeps the transistor on so it is not a problem. If the VR is turned up too much, the transistor will be turned completely on and the signal will run out of head room. I toasted my transistor this way and had to replace it.

Here is a post about how I adjusted the bias on mine.
Post in thread 'Palomar RFX95HD' https://www.worldwidedx.com/threads/palomar-rfx95hd.234665/post-810860
 
Ok, here is what I have done so far:
Reworked the variable key mod someone else did. It was wrong in my book.

They had 2 wires coming off the center pin of the Tip120. One going to the positive of the cap in place of JP36, the other going to the lower pin of the RF Gain control. Removed the wire going to that center leg of the tip120 over to the outer pin of RF Gain control and soldered it instead to the front of the coil L15. I left the other wire on that center pin of the tip120 going to the positive leg of the JP36 cap alone.
The other outer pin of the RF Gain control had a wire going to an IF can, no resistor, just directly to the IF can. I removed it from the IF can and inserted a 100 ohm 1/2w resistor in series with that wire and the IF can.
The center pin of the RF Gain control is wired correctly and goes to the TIP outer leg (correct leg).
The electrolytic cap they placed in JP36 spot was a Chinese knockoff at 1000uf 25v. I replaced that cap with a Nichicon 470uf 25v cap.
I removed C71 (220uf 16v) and replaced with a 47uf 25v Nichicon.

Set the VR on the RFX to the point that my ammeter on my power supply just started to rise off the 1A scale when keyed. Pretty much landed in the factory spot it was originally from the factory.

Checked the SWR scale adjustment to see if it had been tinkered with, and noticed someone had it cracked all the way up. Unhooked the 8v line to the amp and reset that adjustment to correspond with my external SWR meter. Hooked 8v line to amp back in line. SWR now reads just a tad above 1:2 with amp running.

Variable key now works fine with the amp, just gets slightly muffled when turned down below 3w swinging 50w.

Still only seeing 50w max peak out the RFX, and meter light doesn't dim that much any more, still dims but not as much as before, amp runs cool to luke warm.

Only thing different now is xmit audio is somewhat bassy. I'm using a stock superstar handmic, as I do on all my radios.

Ran out of ideas as to why I'm not seeing full output, other than my DC wire that I use. Gonna go pick up a better quality power wire from our local Pilot or QT truck stop up the road and try that.

Everyone said it still sounds awesome and is holding a strong steady signal, with 2 S-Units of swing on their ends.

I hate having to fix other techs mistakes (like this var. key in this one was), cause I don't know what other mess they tinkered with.

Any other suggestions you guys?
 
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Update:

Replaced flimsy power cable with the CB3AXX 12ga 10a 3 pin 2 wire dual fused heavy duty power cable today.

Results:
On the cobra 29 Ltd classic with the new RFX95HD installed, only 60w peak swing, meter light barely dims now. But still nowhere near the output it should do.

Tried my 949 with the RFX75 installed, only seeing 60w peak swing, meter light barely dims now. But still nowhere near the output it should be.

My desk setup:
2 Power supplys,
1 is a pyramid phase 3 at 35a,
1 is a yaesu 35a power supply.

1500w old school MFJ dummy load.

6" (inch) jumper from dummy load to watt meter.

6' (feet) jumper from watt meter to RF sampler. Sampler is a straight through circuit for this purpose.

6' (feet) jumper from RF sampler to radio.

6' (feet) CB3AXX heavy duty 12ga 10a power cable from either 35a power supply.

Cobra 29, no mods other than variable key and RFX95HD. Keys 5w, swings to 22w peak.

Galaxy DX 949 with a couple audio circuit mods and RFX75.

Watt meter was bought new by me straight from MFJ. Never tinkered with.

Oscilloscope corresponds with my watt meter.

Tried 3 different mics, 1 stock superstar mic, 1 stock cobra mic, 1 D104 575-M6B.

I'm stumped, not sure why I'm not seeing the full output. I'm out of ideas.

Thank you all once again.
 
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Well,
Swapped out the MFJ 872 meter for the big screen MFJ 868, now I'm getting better readings but strange:

The 868 requires a 12v adapter plugged in the back to work.

The Cobra 29 LTD Classic with the RFX95HD is now showing around a 17w deadkey, swinging 97w peak, swinging forward up to 40w average.

Whereas,

My Galaxy DX 949 with the RFX75 is now showing around A 13w deadkey, swinging up to 120w peak, swinging forward up to 30w average.

Could my 872 MFJ meter have been my problem the entire time?

Before I swapped meters, I ran the radio jumper straight to the watt meter (872) and saw the same results as my previous post stated. Only after swapping meters (872 to the 868) did things start showing around the right output. But the 872 is a brand new meter, the 868 is used but I'm the second owner.

If the above results look right to you guys, then why would the RFX75 on the DX 949 show 120w, whereas the RFX95HD on the 29 LTD show 97w?

I feel more comfortable with the 868 readings, but confused as to why the RFX75 is showing a lot more than its advertised and compared to the RFX95HD showing about what the advertised output should be?
 
So the 868 meter seems about right to readings on your meter as far as the 29/rfx95hd? 17w swinging to 97w peak?

Still curious about the rfx75 on the 949 showing way more than the 29/rfx95hd.
 
Just hooked a different cobra 29 LTD Classic without an rfx hooked to the 868 meter, it shows this barefoot 29 keying 5w and swings up to 40w peak.

Took cover off and checked to see what had been done. All I noticed was another sloppy variable key job and D11 cut, along with the slug for the coil in front of the final was removed. It has a 2029 final in it.

Does 40w peak sound right for a cobra 29 with a 2029 final in it and D11 cut?
 
Just hooked my single final 959 (1969) up to the 868, it shows about 28w peak. So I guess the 868 is showing about right. Whereas this same 959 On the 872 only shows 20w peak.

The MFJ 868 says it's a True Peak Reading meter, not sure the difference in the 872 peak meter, which doesn't say True Peak Reading.

Gonna stick with the 868 I guess.
 
Just did a comparison between 3 different MFJ meters, 2 small (870 and 872 grand masters) and 1 large (868). Only thing I changed between tests were the meters and 4 different radios.
Here are the results:

MFJ small 870 & 872 meter vs MFJ large 868:

Cobra 29 LTD:
870/872 Peak = 22w output
868 Peak = 40w output, bout what I see others getting on this type radio using Bird 43 meters on YouTube.

Galaxy DX 959:
870/872 Peak = 20w output
868 Peak = 30w output, bout what I see others getting on this type radio using Bird 43 meters on YouTube.

Cobra 29 LTD/rfx95:
870/872 Peak = 55/60w output
868 Peak = 97w, right in the ballpark, and bout what I see others getting on this radio setup using Bird 43 meters on YouTube.

My 949/rfx75:
870/872 Peak = 50w output
868 Peak = 120w output, my personal modified radio, lol..., only saw 2 others using this add-on amp getting around the same thing using Bird 43 meters on YouTube.

I did notice that if you multiply the 870/872 peak readings by a factor of 1.5, the numbers line up almost perfectly with what these radios should do on Bird 43 meters. Except my personal 949/rfx75, lol...

And also the average readings from the large 868 meter are bout the same average readings as I see others are getting with these radios/setups on Bird 43 meters on YouTube.

Yep, sticking with the 868 big screen.
 
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Do like the profesionals, use the meter that shows the biggest number and smile.
My mfj 2000 cross needle has a stingy spot around 800. My white face dosy with the 1/4 phono jack shows 60 on those kits. anothrr meter shows 80 and yet another shows 100 but all will show the same one some things some days. How much effect does tempature, humidity reflect have on the readings? I have put an anylizer on some hamfest dummyloads with 1.6 swr.
 

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