What is this mod? Stryker 955

[Justme]

Simple, getting 130 watts out of 2 of these switching fets is madness, they are made for 65 watts dissipating power at 25 C and that degrades every 1 C with 0.5 watt, that goes for the chip structure inside the fet, that has to be transfered to the hot tab on the fet then through an isolator to a heatsink.
that is 1 x 20 degrees difference for every transition before the heat from the chip reaches the heatsink.
That amp is running literarely on it's toes, and only run for very short times for a reason, or else smoke would come out.

There is a reason CB uses cheap solutions sold as amateur radio or not.
And there is a reason real ham radios have a totally different approach to making P.A.s build to last and spectral purity, hence cost more.


I rather have an decent designed P.A. with real HF fets, with a lot of headroom made for continuous use on the set power output like the 991 A or FT2000-D has with 4 Fets.

 

[Handy Andy]

Another look, using the 955 -


It's Q56 - but the design above is complicated by the switched SSB power...

But note the novel use of D35 and D48...

D41 simply keeps Q56 from blowing up (reverse bias) - removing D41 disables the circuit, but shorting out D41 (Dangerous but possible) then makes the Envelope tracking far more aggressive. This would help those looking for a level of Compression that would help drive comp amps...removes the "swing" Makes it worse actually but the audio "pinched" effect is there - some do not like that effect - so you have been warned...

 

[loosecannon]

is it possible that the resistor used in a standard NPC mod has been made variable and mounted on the outside of the case?

i really don't know too much about these radios.
LC

 

[Handy Andy]

They're an SMD nightmare...

Remember the 2999 conversion and how they squeezed that in?

Similar in sizing (.060 to .040) for parts as RCI's 2995 and similar 6950XX boards...Shielding and all...

Woof...

In reference to the NPC mod, there's no swing in the Dosy (YT) to verify that - NPC should have been all forward - with tone? - can't verify...Throw a thermometer on the back panel to see those effects...

It's my thinking that Q56 is used as a variable Envelope Power for both the AM, FM "sides" control the compression of the audio onto the Bias..so it would not be too far off to think NPC, but the audio heard or if it's even monitored - is not possible to tell from the vid.

I can see where the NPC side, (the 560 ohm reference) can be made variable along with the Envelope control - so the level of audio injected, or compressed - depending on how you look at it - will affect the drive of the tone but without any swing to show - no true method I can see except for taking the internal trimmers and moving them outside "to see what she can do" approach.

 

[Shockwave]

If 11 meter operators would stop buying "high power" radios with switching FET's, you could force these manufactures to spend another $60 to install real 12 volt RF linear MOSFETS like like HF mobile gear runs today. I'd pay the full cost of that increase to get a real linear amplifier and won't touch one of these rigs as they stand now. Especially if you plan on using it to drive another amp and take the "dirt" up another 13db or more.

Keep buying PA stages with 99 cent transistors in them and they will keep making them for you. Demand better because we have taken a major step backwards in reliability and signal purity using power supply transistors as linear amplifiers. No other band but 11 are using these devices in linear mode. They have targeted us because... well, most of us don't know better. No offense meant.

 

[Shockwave]

There is no magic here because you really only have 3 options to control power output on AM. You can adjust drive which impacts carrier and PEP proportionally. You can adjust carrier which is independent of PEP or you can adjust audio compression which will clamp PEP independent of carrier. The rest is all sales talk. As someone else said, "where is the scope" so we can see in real time what is going on between the carrier and tone peaks? Even more concerning is testing is being conducted with a 1000 cycle tone but the spectrum analyzer is showing one fuzzy, wide peak....

If it were showing a clean 1000 cycle modulated AM signal, you would see that one spike much sharper with two smaller bumps to each side, 1000 cycles away from the center carrier. Where are the well defined sidebands that we should be seeing under single tone test on AM??? Open up the bandwidth on that analyzer and start showing the harmonic content at multiples of the fundamental frequency and you might find the problem or worse yet, an oscillation.

PS: If you're testing on a dummy load, you should go through an antenna tuner so that you can simulate the conditions of a resonant antenna rather than a wideband load. This is where trouble begins to reveal itself.

 

[loosecannon]

Thanks for replying Shockwave.

It was the compressor circuit that i didn't take into account.
i guess that's why i was guessing about an NPC mod having been done.

I couldn't agree more about putting up with crappy parts in a pretty box.
somehow i don't see sales slowing down enough to warrant a change on their end.

people like to buy new radios, what're ya gonna do.

the in-band distortion was something that i noticed, but didn't want to be the first one to comment on LOL.

i do understand that many people in the hobby just aren't concerned with spectral purity, or what the sinewave looks like on the scope.
to each their own, im just glad to know what was actually done to the radio.
LC

 

[Justme]

The remaining hard core 11 meter users here know they can get a fine for 2500 up to 25.000 Euro for an illegal station, and don;'t want to cause interference in neighbours equipment so they buy entrance radio's for hams, running them with a clean signal of 100 watts out knowing the chance of causing trouble is small.
Better as a souped up 11 meter radio causing all kinds of trouble, in our densly populated country.

I can run 1000 watts from my Heathkit SB-1000 without causing any trouble and have been doing so for the last 32 years i live here on the edge of our city.
On 2 meter my homemade 160 watt A/B transistor amplifier is clean as a whistle, build that 35 years back from the Motorola handbook with 2 x MRF 247 Class A/B transistors.

 

[Shockwave]

The in-band distortion was something that i noticed, but didn't want to be the first one to comment on LOL.

I'm not sure if the tone is being listened to through an on air monitor but in any event, just my ear can detect that there is distortion present in that tone at many points during the test. At this point, I'm unable to confirm if that distortion is present in the TX or only in the recorded audio although, the analyzers absence of clean sidebands with a single tone, is suggesting where the problem is. It has the distinct sound of square-wave and that does make meter readings look more impressive when a scope is not present to reveal what is actually happening.

I do understand that many people in the hobby just aren't concerned with spectral purity, or what the sinewave looks like on the scope. To each their own, im just glad to know what was actually done to the radio. LC

Once people grasp the concept that a signal that is twice as wide, is only half the strength at any given power level, they might become more concerned. This is also just one reason why HiFi modifications should be switched out of line in favor of communications grade audio, when working difficult or competitive DX conditions. The idea of placing twice the bandwidth on the same size carrier is absolutely counterproductive here because for one, it causes a 3db drop in signal strength under ideal conditions. That problem gets much worse once you understand how "selective fade" impacts any DX signal, proportionally to its bandwidth.

 

[loosecannon]

HiFi modifications should be switched out of line in favor of communications grade audio, when working difficult or competitive DX conditions. The idea of placing twice the bandwidth on the same size carrier is absolutely counterproductive here because for one, it causes a 3db drop in signal strength under ideal conditions. That problem gets much worse once you understand how "selective fade" impacts any DX signal, proportionally to its bandwidth.

Don't want to derail my own thread, but i think the needed info is already in here.

Just wanted to say that is exactly what i found through experimenting with the wider banded audio mods.
the radios just can't hear that same sharp 1K tone at the same low input level of an unmodified radio.
Sure, the people that you do hear can sound much more pleasant, but there is absolutely a sensitivity trade off.
how much of a trade off is probably up to the individual operator and how they run their radios.

as an example, for an MB8719 type radio, it's not unheard of to hear the tone down at -125dbm. (30% modulated).
with a widebanded radio, you are looking at somewhere around -121dbm, or even maybe -118dbm where the tone really starts fading out.

i guess the way to compare how wide of a frequency range you are transmitting with to how effective your signal is on the actual channel you are on is to compare it to running a beam antenna as opposed to a groundplane (idk maybe that's a terrible comparison).
LC

 

[dieseldriver]

I would like to see this thing on a scope. I don't believe its possible to raise avg power and lower peak power without flat topping. Its the same waveform measured two different ways after all. It would have to be some kind of compression like on an audio signal, except done on the PA stages? Is that possible?

BBI's video about it shows it on a scope.

It looks absolutely horrific. But to his credit, he also says the radio is never going to go on the air toward the beginning of the video, it's strictly a bench radio, and he got it so he can emulate several different radios with one unit instead of having to have 5 or 6 different radios to show how they'll affect output power of a given amp.

 

[Tokin]

So its just as i said, its his new ghost watt generator. Crap in equals amplified crap out.

 

[davew41]

go look at d-rails original video he shows the same radio before it ships to bbi look at his ANALYZER settings lol 30.0000 YES A WHOLE BAND and more and he says it is clean? pause the video at 2:03 your answer is there RIGGING the equipment

 

[davew41]

always watch the settings they are hiding snake oil right in front of you
There is a good reason D rail is not showing the scope he cant show this mess
he also charges for a hi fi receive and hi fi audio mod ( 120$)

 

[Shockwave]

The most surprising thing to me is that this feels like something new to so many people. That is likely due to the fact many have become accustomed to completely disabling the AMC limiter in radios. This circuit not only prevents distortion on word peaks but it's also a very effective way to hold PEP output, within a well defined limit. That feature alone can be invaluable when trying to set a rig to properly drive a linear amplifier. The same holds true for ALC on HF rigs and SSB use.

If you don't like the setting or range of the existing circuit, consider adding resistance to the "trigger" or sensing diode in order to increase range, long before you just hack the circuit out of line.