Avoiding Splatter, RFI and other

[Wire Dawg]

I missed the exact frame of the live broadcast when N. Armstrong stepped on the moon in 1969, due to a CBer's untimely TX. Since those early days, I resolved not to allow my station to become a nuisance. I'd like to know of all the practices that may lead to RFI and splatter, what brand/model equipment is more prone to cause RFI, and perhaps compile a list of tricks, practices and methods that you may have used (or recommend).

Grounding the tower or mast as well as grounding the radio and peripherals have been my first line of defense. I know that the 'grounding' issue may fill pages as a topic. I've used the 'ugly' balum (choke) with good results on my dipoles and an old Penetrator 500. Ferrite beads work but not always provide the desired effect. Good coax and solid solder of connectors have helped. Do you suggest to steer clear of certain radios, microphones, linear amps or antennas (I'd like to know if export radios are prone to RFI after conversion). I'd also like to know if there are any specific component-level mods that promote these nuisances. Any suggestions regarding how to avoid RFI, splatter or bleed-over are welcomed.

 

[mr_fx]

well this is a simple one, avoid Slattennas, like the Imax, or worse yet the A99

stop running c class and worse amps

ground your junk

stop over driving you amps... a 2sc2290 does about 60 watts PEP @ 12.5v, a mrf455 does about 60 PEP @ 12.5v, a 2sc2879 does around 100 PEP @ 12.5v. Upping the voltage to 13.8v will yield a 9-11% increase, over rated output, and yes the output increase is linear.

If your meter tells you that your 4 x 2sc2879 is putting out 900 PEP it is reading 500 watts of trash and at best 400 watts of actual power

Anything above the rated power output is not what you want, it's just trash out

 

[W5LZ]

Any radio, export or not, is subject to producing unwanted signals when modified incorrectly. That means you can't expect miraculous power increases with only changing a part or two or clipping something. There are definite limits and pushing those limits always produces garbage. So don't expect something for nothing.
There are NO standards for export radios or for 'CB' amplifiers. There are no 'purity' requirements and never have been. Expecting 'standards' for 'purity'/'clean' 'CB' amplifiers is a joke. There are no 'secrets' about building good amplifier, the various transistor and tube manufacturers give specs for their products, and with a little knowledge about what those specs are and common amplifier circuits, producing a good amplifier shouldn't be difficult at all. But there won't be as much profit if it's done right. There's the 'catch', profits. Draw your own conclusions, but try to be a little realistic about it.
- 'Doc

Psst - All those 'cures' you see/read about are to clean up a dirty product.

 

[IRock817]

I have real good luck with a RCI 2995 DX and a RCI 2950 DX. Modulating with a home made compressor/processor with built in echo ( for texture an depth) on the 2995! Simple external echo on the 2950! Both radios driven with a silver eagle. A little mobile four pill for help. The best part is we are rx/tx with one of the best ground planes made to date, the Penetrator 500.
Every piece in my Jewel box is older and used, except for the processor, which was designed for my station.
The P500 was bought used from a guy that had it up for many, many years. I totally disassembled it and made it better then new with some upgrades.
So to make a long story longer and kinda answering the thread, my closest neighbors home is thirty five ft. from the antenna, and two years ago I went and asked them if my station was bothering them and they looked at me like "what are you talking about"!
Good coax, equipment and to know what ninety or ninety five percent modulation means makes all the difference!
Ground everything, and bond! Break up guy lines and all!
Take your time, do it right the first time, and have fun!

 

[Wire Dawg]

I agree with the 'dirty' amps comment. The desire for better qso's and DX has been muddied by many with the blind pursuit for squashing power. The loss or lack of etiquette/ decorum by some CBers just compounds the splatter/ RFI problem. Since several export radios are sold for the 10/12 meter bands, I wonder if those with high output would be built with cleaner amps than the class C linears sold to fuel the power craze? I saw a RCI 2950 that was converted and tuned to 11 meters, but without peaking factory power. It sounds very clean and has no bleed-over. The radio is not grounded to a tipical ground rod, but it's connected to a piece of coaxial braid that just lays flat on the floor, and the mic gain set at the 12 o'clock. Are there some export radio brands more prone to RFI after conversion than others? How do you find a reliable tech to perform a good tunning & alignment? Thanks

 

[RatsoW8]

well this is a simple one, avoid Slattennas, like the Imax, or worse yet the A99

stop running c class and worse amps

Of course junk band amps are a big issue for other reasons but I'm curious how an A99 or Imax 2k cause problems in themselves. That is if the antenna is tuned correctly and a relatively close match SWR wise. How is the 100 watts from my dipole less likely to saturate someones cheap home phone that 100 watts radiating from a resonant A99? I think it the strength of the RF field and not the radiating antenna causing the problems.

Seems that more often than not cheapo electronics that have no shielding or immunity to even low legal CB levels of RF are usually to blame.

 

[BumpStart]

Lol.. When I first read this post yesterday I just knew that the Hambone types were going to jump all over it..

 

[jazzsinger]

I missed the exact frame of the live broadcast when N. Armstrong stepped on the moon in 1969, due to a CBer's untimely TX.

can't help asking, but did that cb'er key up outside your property and mess up your tv pic, or was he keying up outside the hollywood studio where the moon landings were faked from?

man on the moon in 1969, lol, this is most likely what their onboard computer looked like;

 

[jazzsinger]

Of course junk band amps are a big issue for other reasons but I'm curious how an A99 or Imax 2k cause problems in themselves. That is if the antenna is tuned correctly and a relatively close match SWR wise. How is the 100 watts from my dipole less likely to saturate someones cheap home phone that 100 watts radiating from a resonant A99? I think it the strength of the RF field and not the radiating antenna causing the problems.

your dipole is a balanced antenna, whereas the A99 or I max are seriously unbalanced, which in turn can cause coaxial radiation which is highly undesireable and can cause rfi all over the place, things might not have been so bad if they had actually supplied counterpoises with those antennas rather than try to rip more money out of people.

rfi isn't always relative to signal strength (i've seen many cases where a tweaked cb caused havoc but a standard one or ham rig running 100w did nothing), can be caused by dirty weaker signals or even in the case of the A99 etc from coaxial radiation close to the appliance suffering rfi, poor design of both the radio or interfered with appliance is another very common cause of rfi. even a corroded contact can act as a rectifier and rectify rf in an appliance or even cause rfi to the radio.

 

[psycho]

well this is a simple one, avoid Slattennas, like the Imax, or worse yet the A99

stop running c class and worse amps

ground your junk

stop over driving you amps... a 2sc2290 does about 60 watts PEP @ 12.5v, a mrf455 does about 60 PEP @ 12.5v, a 2sc2879 does around 100 PEP @ 12.5v. Upping the voltage to 13.8v will yield a 9-11% increase, over rated output, and yes the output increase is linear.

If your meter tells you that your 4 x 2sc2879 is putting out 900 PEP it is reading 500 watts of trash and at best 400 watts of actual power

Anything above the rated power output is not what you want, it's just trash out

Does that mean I am going to HELL because I run a class c amp? Back in the good ole days people hooked up their radios/amps and as long as they sounded good, they couldn't care less about splatter and harmonics.
Just set the shit up to sound good and relax.
If someone is worried about bleeding over a few channels then they need to cut the modulation back to 80%, problem solved. There is enough to worry about in day to day life, worrying about this is just silly.

 

[Shockwave]

can't help asking, but did that cb'er key up outside your property and mess up your tv pic, or was he keying up outside the hollywood studio where the moon landings were faked from?

man on the moon in 1969, lol, this is most likely what their onboard computer looked like;

I have noticed a good portion of the younger generation today also believes the moon landing was faked. It's usually based on some shadow that doesn't line up right or the stiff flag that was pictured. Keep in mind several people gave their lives to reach that goal over a decade period. As time passes we tend to forget about things like the laser reflectors strategically placed on the moon that we use to monitor the exact distance. NASA openly admits the computer used then was so primitive today's wrist watches are more powerful. Remember the computer crashed on Apollo 13 due to lack of battery power and it was actually flown through reentry completely by eye with no computer guidance.

As radio operators we should also consider the communications link that was in place around the world to limit the times loss of signal would take place. More importantly that there were several hams with the capability in 1969 to monitor those communications first hand with large arrays pointed directly at the moon. If it were faked, why continue to fake it several more times right through the Apollo 13 accident? What about the nearly 1000 pounds of lunar rocks brought back that date 200 million years older then anything ever found on earth? Let's not forget so quickly.

 

[mr_fx]

Does that mean I am going to HELL because I run a class c amp? Back in the good ole days people hooked up their radios/amps and as long as it sounded good, they couldn't care less about splatter and harmonics.
Just set the shit up to sound good and relax.
If someone is worried about bleeding over a few channels then they need to cut the modulation back to 80%, problem solved. There is enough to worry about in day to day life, worrying about this is just silly.

I see no problem with Class C on FM or CW, but on AM and SSB it's just nasty, and when it starts interfering in other bands... I know some people don't care about that, but some people also pee and poo their pants and eat their boogers, it's good for them, but it sucks for the people around them.

it's not just bleeding other channels, it's bleeding other BANDS, interfering with emergency communications, all so you could run an amp that made 5 more watts...

 

[Ratfink]

I see no problem with Class C on FM or CW, but on AM and SSB it's just nasty, and when it starts interfering in other bands... I know some people don't care about that, but some people also pee and poo their pants and eat their boogers, it's good for them, but it sucks for the people around them.

it's not just bleeding other channels, it's bleeding other BANDS, interfering with emergency communications, all so you could run an amp that made 5 more watts...

It's not only class c that is the problem crap tuned radios are about 75% of it then you have your spurious emissions from your 2950 style radios that are a huge problem not matter linear/non linear amp is behind it. But if you put clean in clean out and proximity isn't an issue your usually pretty good

 

[Ratfink]

Does that mean I am going to HELL because I run a class c amp? Back in the good ole days people hooked up their radios/amps and as long as they sounded good, they couldn't care less about splatter and harmonics.
Just set the shit up to sound good and relax.
If someone is worried about bleeding over a few channels then they need to cut the modulation back to 80%, problem solved. There is enough to worry about in day to day life, worrying about this is just silly.

And percentages of modulation has nothing to do with anything . Mod can be in the 200% range cleanly but most would say 150 or less is the better way and most radios will not produce clean mod past 80% without some modding .

 

[Captain Kilowatt]

And percentages of modulation has nothing to do with anything . Mod can be in the 200% range cleanly but most would say 150 or less is the better way and most radios will not produce clean mod past 80% without some modding .

Let us not forget that that 150% or 200% modulation pertains to ONLY the positive peaks and NOT the negative peaks.It is negative modulation in excess of 100% that causes carrier cut-off and distortion/splatter. Commercial AM broadcast stations routinely run asymmetrical modulation of 120% positive while maintaining 100% negative mod. I had a problem with the modulator in a Nautel Amphet-1 transmitter one time and tested it to 100% neg/200% pos modulation when I was done repairing it. The 'scope sure looked weird and that SOB was LOUD as hell on the air..........errrrr......make that the dummy load ......... but clean.