2970N2 Strange Problem

[Mudfoot]

I just bought a brand new peaked and tuned 2970N2, hooked it up to my Ameritron AWM-30 twin needle meter fed into my Gainmaster. My vertical normally has a flat SWR. I have a room full of CB's, exports and a few HF rigs that I play on it from time to time. My CB's and exports are fed into my RM Italy HLA-150. Again, My meter is nice and flat with everything I use on that antenna. My station has an adequate ground. Never had any issues. My analyzer shows love for the Gainmaster.

Well, I hooked up my new 2970N2 an my SWR shoots up to 2.0:1. I get garbled SSB audio. AM audio seems fine. The last Ranger that was on this antenna was an 2950DX. It had no issues.

I must be getting some kind of RFI or something. When I feed the radio directly to the antenna and use the built in bridge, it shows the same SWR problem.

Any ideas? wonder if the rig is spewing some harmonics?

Strange, this is the only radio that has an issue attatched to the GM.

 

[Robb]

I just bought a brand new peaked and tuned 2970N2, hooked it up to my Ameritron AWM-30 twin needle meter fed into my Gainmaster. My vertical normally has a flat SWR. I have a room full of CB's, exports and a few HF rigs that I play on it from time to time. My CB's and exports are fed into my RM Italy HLA-150. Again, My meter is nice and flat with everything I use on that antenna. My station has an adequate ground. Never had any issues. My analyzer shows love for the Gainmaster.

Well, I hooked up my new 2970N2 an my SWR shoots up to 2.0:1. I get garbled SSB audio. AM audio seems fine. The last Ranger that was on this antenna was an 2950DX. It had no issues.

I must be getting some kind of RFI or something. When I feed the radio directly to the antenna and use the built in bridge, it shows the same SWR problem.

Any ideas? wonder if the rig is spewing some harmonics?

Strange, this is the only radio that has an issue attatched to the GM.

That would be my guess.
Did it get 'SuperWhackPacked'?

 

[Mudfoot]

I didn't order a whack pack...

When I key this radio up near my other rigs they all go nuts. My 590 picks it up all the way down to 160 meters. I'm transmitting into a dummy load.

When on my vertical, I show a 2.0:1 with just 10 watts drive. As I slowly turn the power up, the reflection increases until it hits 30 watts, then the reflection decreases.

I had an earlier version of the N2 and never had any issue with it at all, but I had an IMAX then.

I think this radio needs to make a return trip to the vendor or back to the factory.

Sumpin ain't right...

 

[TB01]

What's your minimum and maximum carrier wattage showing on your meters?

 

[Mudfoot]

10 watts low
50 watts high

 

[Robb]

35-40 amp power supply?

 

[Shockwave]

Am I the only one noticing that just about every new high power CB that uses MOSFET's is failing regularly? The Magnum HP, the N2 and several others are all receiving SWR complaints, power dropping off, and that's if they don't blow up in the first 10 minuets of use.

This is what happens when dishonest people market cheap power supply transistors as high power RF devices up to 30 Mhz. The stability and reliability go to hell real fast while most operators think it's an antenna problem because of the effect on SWR.

 

[VA3ES]

From your description, it sounds like something in the TX RF chain is going spurious. Those spurs cause anomalous SWR readings and seem to be producing trash all over the HF bands. Either need the TX RF chain retuned or some component is failing. How is it on a dummy load?

 

[Wire Dawg]

Recently started a thread asking whether the use of an antenna matcher would resolve the high SWR that has developed between my n2 and the amp. It also appears to be demanding more and more amps out of the Astron, at the same output level. After writting the symptoms to Ranger, the technician indicated that the radio probably needs an alignment.

 

[Mudfoot]

The only time I've ever seen anything close to these symptoms is when I've had RF issues in the shack.

This is close, but not quite. I know my antenna systems are good. I think shockwave has the ball on this one. I owned an N2 about 2 years ago, but it worked fine and was a decent performer. It was a fun rig on CW. I sold it and have been wanting to try the newer green on black version.

I placed it inline with my meter and dummy load and everything seems to work fine. I noticed no issues. I hooked it up to my 10 meter wire and noticed the reflection will decrease when I talk. There is a sweet spot in the RF power pot that will produce crappy audio and mic squeal when adjusted between 20-30 watts DK.

I haven't talked to the vendor I got it from yet. It also came with the warranty seal cut. Most dealers put a new seal on after they convert and align. I don't know how this will affect my warranty prospects.

Regardless, this thing is puking spurs for sure.

 

[Mudfoot]

35-40 amp power supply?

Tripp-Lite PR-50

 

[VA3ES]

While all antennas can be tuned for a low SWR with a clean and non-spurious radio, the spurious radio will be unstable and very sensitive to reactances in the antenna. Thus, different antennas (all showing low SWR) will react differently with the spurious radio. If the radio is wonky and spurious with any antenna, putting a dummy load in line will always show 1:1 because a dummy load is flat across every frequency. The high SWR comes from a product outside the antennas range. With the dummy load, everything, everywhere is 50 ohms. If trying it with a dummy load shows no problems, then it probably is spurs. Let the factory techs handle it. When you send it back, explain the problem. The techs need to do some detective work. Just putting it on a dummy load, finding nothing wrong, will only aggravate you!

 

[Shockwave]

I doubt these problems will improve significantly until the manufacturers of these high power radios are willing to spend $50 to $100 on a pair of decent transistors in the push pull output stage. It would seem the "engineers" making this equipment are doing exactly what VA3ES said and only checking these radios on a dummy load. Wouldn't be a problem if they used a spectrum analyzer along with the dummy load but they obviously are not.

If the variable power control on one of these radios cannot produce a continuous, smooth change in power throughout its range, the RF amplifier is malfunctioning. This means no spikes in power or SWR at any point throughout the adjustment and must be done into resonant load like a tuned antenna. Thinking you've found one spot that it may run stable at can be misleading. Even if the carrier looks stable, once you modulate it or use it on SSB the output may regularly transition in and out of the unstable condition.

 

[Robb]

Am I the only one noticing that just about every new high power CB that uses MOSFET's is failing regularly? The Magnum HP, the N2 and several others are all receiving SWR complaints, power dropping off, and that's if they don't blow up in the first 10 minuets of use.

This is what happens when dishonest people market cheap power supply transistors as high power RF devices up to 30 Mhz. The stability and reliability go to hell real fast while most operators think it's an antenna problem because of the effect on SWR.

Well, the upside with MOSFET's is that they are cheap and plentiful.
One can buy a grip of them with a ten dollar bill.

I think that most of the problems that happen with these devices occur at the user end. You know what I mean. Among the first things hackers do is yank out the AM Limiter like it was a bum tooth. The next thing they do is spread the 54mhz trap coils to see more watts - lol. Finally, they turn up the the power output using a non-peak reading meter - a Dosy or some similar junk meter - to gauge the radio's output. Of course, the Dosy cannot read peak watts - so the end result is that those MOSFET's are set way too high/hot and running on the ragged edge before they fail. Then they fail. No small wonder that they last at all when given those abuses. Radio operator calls 'foul' on the mfr. So it goes - until the repair shop tech that fixes it sets it straight and warns the operator not to mess with the radio any more once they've fixed it. Do they understand or listen? No . . .

 

[Mudfoot]

Other thing I noticed is the VFO knob is sloppy and turns rather easily. I've had a few of these type rigs over the years. The knob was always nice and tight with very discernable clicks. This one has 1/8# slop and is extremely easy to turn. You can barely feel the clicking.

I don't know if the new ones are this way or not. Can anyone with the green on black display comment on the channel knob?