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Fact or fiction
- Thread starter Ziploc
- Start date
My dislike for exports started with an old school rci 2970. I read something online about them and the 2950 transmitting spurs on the 10 meter band. I tested mine and found it to be true. You could hear it crystal clear on 10 and 11m. The signal on 10m was weaker but still a s5 a few miles away.
A friend bought a 2970n2 a few years ago. They have improved but I can still hear some noise on 10m when his mobile was close. Same for a base 5 miles away using a 2995.
Here is a YouTube vid that explains what's happening. I've also heard motor mouth maul speak of this. He stopped using an export with his mauldulator for this reason
The largest mobile amp I had was a 16 pill used with various drivers. I had less issues with the cobra 29 and saw more average power. The exports I've used are the galaxy 95t, connex 4800, magnum s380 and the magnum s9. The s9 was my favorite radio but I still kept coming back to the cobra 29. I will say the magnum s9 and 4 pill xforce was a sweet combination.
There's something about high level modulation with a modulation transformer that just works. The waveform can look like a picket fence and not sound as distorted as an over modulated export. It may have something to do with the type of distortion created by baselining the carrier with a mod transformer vs transistor. Something similar to the guys that think tube amps have better audio. There is no difference until the device is driven into compression. The distortion from the tubes doesn't sound as crappy. The cobra 148 was another one I really wanted to like but the mic gain settings were too finaky. I could run it wide open barefoot but had to cut it back with the amplifiers on.
I don't have the equipment to prove my theories of the exports being dirty and most of my cb gear is collecting dust these days. The exports just seemed to have lower average power, cause issues with swr, oscillations and be finaky about the mic gain settings. With a cobra 25 or 29 I can install variable power, leave the mic gain wide open and they sound good with any amp I put behind them.
It doesn't do anyone any good to be transmitting on another band. The amplifiers and antennas are not tuned for the frequencies the spurs are on. If the amp is amplifying multiple signals it will run hotter. This issue is compounded by the amp being out of tune on those other frequencies.
A friend bought a 2970n2 a few years ago. They have improved but I can still hear some noise on 10m when his mobile was close. Same for a base 5 miles away using a 2995.
Here is a YouTube vid that explains what's happening. I've also heard motor mouth maul speak of this. He stopped using an export with his mauldulator for this reason
The largest mobile amp I had was a 16 pill used with various drivers. I had less issues with the cobra 29 and saw more average power. The exports I've used are the galaxy 95t, connex 4800, magnum s380 and the magnum s9. The s9 was my favorite radio but I still kept coming back to the cobra 29. I will say the magnum s9 and 4 pill xforce was a sweet combination.
There's something about high level modulation with a modulation transformer that just works. The waveform can look like a picket fence and not sound as distorted as an over modulated export. It may have something to do with the type of distortion created by baselining the carrier with a mod transformer vs transistor. Something similar to the guys that think tube amps have better audio. There is no difference until the device is driven into compression. The distortion from the tubes doesn't sound as crappy. The cobra 148 was another one I really wanted to like but the mic gain settings were too finaky. I could run it wide open barefoot but had to cut it back with the amplifiers on.
I don't have the equipment to prove my theories of the exports being dirty and most of my cb gear is collecting dust these days. The exports just seemed to have lower average power, cause issues with swr, oscillations and be finaky about the mic gain settings. With a cobra 25 or 29 I can install variable power, leave the mic gain wide open and they sound good with any amp I put behind them.
It doesn't do anyone any good to be transmitting on another band. The amplifiers and antennas are not tuned for the frequencies the spurs are on. If the amp is amplifying multiple signals it will run hotter. This issue is compounded by the amp being out of tune on those other frequencies.
Yes , I was up Dustin’s and his customers radio for radio the cobra and uniden were out talking the big exports. This one combo was. 29 comp 2 pill toshiba 2879 out talking a ranger b4 like it was stock lol
This is another fishing story that doesn't prove anything. Another friend of mine used to put an a99 on a 5 foot mast in the stake hole of his truck bed. He would park in an empty parking lot and talk on the radio at night.
I stopped to see him one night and he wanted to drag race. He had a 1x4 with a new version superstar 3900. I had a puck mounted predator 10k, uniden 76 and a 2 driving 16. That wasn't fair so we did it barefoot and I won. The people listening all over town said I was wiping him out.
His radio made more power, his antenna was bigger and higher. Maybe the a99 really sucks.
Back when pills were cheap and of good quality I would run a 29 into a 1x2 on 20 volts. It was a splattering pig but would clobber the neighbor that ran the 2995 and a 6 pill.
I stopped to see him one night and he wanted to drag race. He had a 1x4 with a new version superstar 3900. I had a puck mounted predator 10k, uniden 76 and a 2 driving 16. That wasn't fair so we did it barefoot and I won. The people listening all over town said I was wiping him out.
His radio made more power, his antenna was bigger and higher. Maybe the a99 really sucks.
Back when pills were cheap and of good quality I would run a 29 into a 1x2 on 20 volts. It was a splattering pig but would clobber the neighbor that ran the 2995 and a 6 pill.
Shadetree Mechanic
Delaware Base Station 808
I run a low pass filter on my station as I was concerned with harmonics on 54 MHz as that is what I have always heard about. I run a Stryker 955 into a 4 pill but I don't want to be on 10 meters with it. I wonder if there is a low pass filter available that would give me the upper channels without being on 10 meters? I might need to re think my station setup.
955 Stryker is clean radio as far as I know, hear them from practically every state in the USA, never heard any kind of bleed over from one
The low pass filters I am familiar with cut off at 30 mhz. That wouldn't help the spur on 28 mhz but is still good practice. It's doable but as far as I know no one sells one. A bandpass filter for the cb band would be nice. I believe Ice Manufacturing used to make one. I don't remember the specs.
My 955 had an oscillation issue and would throw a spur somewhere around 26 mhz. There is a thread I started on this forum somewhere. Another forum member had the same issue. I asked a few people that bought one of they had the same issue. A couple got defensive so I stopped asking.
The audio circuit in the 25/29 radio's is different and/or better then what's in export radio's. I know I am not explaining it correctly but that is why in a shootout most run the old school Cobra/Uniden radio's. We need one of our many techs to chime in here.
BJ radionut
Supporting Member and 6m addict
https://www.dunestar.com/product/single-band-bandpass-filters/
He no longer lists one for 11 meters. However, be easy to configure one to work in that range. I have used one of his for 6-meter filters during Field Day. I had it between radio and amplifier, found it to work very well. It performed well at reducing some receiver noise and sending a clean signal to the amplifier. Worked well at rejecting out of band signals and wide range receiver noise.
Seems like a good guy to deal with might contact him about the special build for 11 meters filter.
These are rated at 200 watts PEP SSB...so no high output rigs or Big Swinger AM'ers...He lists the duty cycle of 100 watts PEP for RTTY/Digital signals...so this would include AM also...IMHO
All the Best
Gary
He no longer lists one for 11 meters. However, be easy to configure one to work in that range. I have used one of his for 6-meter filters during Field Day. I had it between radio and amplifier, found it to work very well. It performed well at reducing some receiver noise and sending a clean signal to the amplifier. Worked well at rejecting out of band signals and wide range receiver noise.
Seems like a good guy to deal with might contact him about the special build for 11 meters filter.
These are rated at 200 watts PEP SSB...so no high output rigs or Big Swinger AM'ers...He lists the duty cycle of 100 watts PEP for RTTY/Digital signals...so this would include AM also...IMHO
All the Best
Gary
What were you running for an amp Gary? A lot of guys think putting a filter between the exciter and the amp is dumb because the amp will "generate harmonics" however a properly run amp will only amplify what it is driven with and using a filter between the radio and amp allows for a much smaller filter and a clean drive signal. That is my plan when I get the Larcan amp up and running. I have a filter I bought from someone online......a ham......in kit form rated at 300 watts IIRC. Hard to get a good 6m filter rated for 1500 watts.
Go here...
https://en.wikipedia.org/wiki/Envel...ower required at each instant of transmission.
Then discuss the efforts of Phase Modulation - rectified into a envelope...
Then compare that to the AM Regulation and it's limitations.
Between the two, you can see where the Diode used in a 29 (READ AM ONLY) radio simply clips off negative going information while passing positive going and DC Bias...
The AM Regulator - has limitations on both POWER is can pass, (Pass Transistor) and the Regulation it needs to provide DC carrier bias - Your carrier.
With these limits - the 29 simply wins due to the level of DC Bias present mixed in with Audio into an Envelope...
Cobra 29 uses 12 Volts - applied to Finals, while AM Regulation uses DC Bias of 4~6 volts (1/2 supply rail) and audio power is impressed upon it...
Limitations begin where the Audio and the envelope easily exceed the ability of the lowered DC bias to handle the power of that envelope sufficiently.
Now...I will also bring up, your 130% Modulation - is possible, but again your DRIVER is the audio AMP Chip and the extra capacitance used to push it onto the DC Bias.
Compare it (Phase Modulation) to the AM Regulation - you see where the voltage multiplication possible thru transformation of DC Bias into a signal applies more voltage and power component than possible with AM Regulations' saturation and the voltage supply for 1/2 the rated per needed carrier to envelope - is more negative going - even when DC bias is allowed to pass.
Now if you rework say, the 148 GTL per this thread Over 130% Modulation there are other efforts you can add into the AM Regulation to help with Envelope - but that can only be discussed once the members understand how dangerous this information can be in the wrong hands...
I was working an Asymmetrical Thread at CB Tricks and was starting to publish works that if used improperly can wreak havoc with Radio communication in general - as not as specifically spurious or harmonic, but as a method of intentional interference if used improperly and not understood.
DISCLAIMER:
If you feel that it would be necessary to delete any more of the posts as I explain my reasoning's, then I will no longer participate in an environment that becomes exclusive to it's members and censors it's own...
Shadetree Mechanic
Delaware Base Station 808
I am checking out the Morgan. The upper limit wouldn't give me 27.555 apparently. I might just get one to try out.
https://surgestop.com/filter-products/m-411cb.html
BJ radionut
Supporting Member and 6m addict
I was running my SS Brick TE Systems HFA amp (Abt 400w PEP) worked great.
Then had one on the 40m xcvr and 75m xcvr also. Our stations were all on a picnic table less than 4 feet apart. We had almost zero cross-band interference even running 500 watts on the other 2 bands. We were very pleased.
We used the DXE models on the other 2 bands (rated at 400 w PEP) they worked very well also in the same configuration. (between exciter and Amp).
All the Best
Gary
A thread here or on a sister site had a post indicating “will work with a request”. (11-Meter plus freeband).
.