50 watt mod? Gimmie the straight scoop...

[Moleculo]

You're correct C2 about under the antenna. The I-10K has barely any RF radiating directly underneath it. However, we all know that even though a dummy load converts RF to heat, it does radiate some RF. That's why I placed the antenna right next to it. In fact, if you drive a KW or so into a dummy load, you might be surprised to find out that you may still be heard within a mile or so. This isn't theory, this is fact that I have personally tested on various HF bands.

In fact, I use a dry dummy load for a 440 MHz antenna for my crossband repeat radio in my house. The radio TX and RX on 440MHz so I can walk around the house using my HT on 2 meters. I get about 4 houses worth of range on the HT if the house radio is TX'ing 5 watts in to the dummy load. Not to sidetrack the thread, but I just wanted to point out that even though dummy load will attenuate RF, putting the antenna right next to the dummy load is a reasonable poor man's test.

 

[C2]

Merely stating that a dummy load radiates some RF makes not point at all. You would need to quantify it in some way. You would need to measure how much of the 32mW harmonic radiated.

Do you have any idea? Can you state wheather or not it was more or less than what was radiated directly under the I10K?

I will repeat your test with a stock Galaxy 949 (optimized and tuned to specification) and a stationary Sony 20" color TV with 1) a rabbit ear antenna and an open dummy load and 2) with a 4 element TV arial and vertical 11 meter dipole arial spaced 40 feet apart at the same height. The TV arial is horizontal and is directed away from the 11 meter dipole. The radio will be keyed under a two tone modulation of 1 kHz and 3 kHz (BTW, you did not mention whether or not you were modulating and how were you modulating, or the percent of modulation). It is already noted that the conducted 2nd harmonic for the 949 is measured to be -62 dBc.

I've done this already and know what it does to my TV, definately it does add some snow and wavyness, even with a stock CB.

What a quandary we have.

 

[Moleculo]

It was modulated using normal voice characteristics into a D104 silver eagle mic.

Dummy loads are designed to not radiate.

That was your statement on why I shouldn't use a dummy load with a TV antenna touching it as one test. I merely explained that dummy loads do radiate some RF. I don't know the specific details of what the ERP being radiated from a dummy load into an TV antenna touch it is. I don't have any way of calculating that, unless I can find ratings on the dummy load (which I'm not going to waste time with). I also don't have any way of comparing that to the antenna directly above the TV unless I model it, which I'm not going to waste time with. I also don't have a way to generate a two tone harmonic. If it's
that important, I'll go get a mobile antenna and figure out some way to make it work in the house so I can put a TV right next to it and do a simple test over again. Also, the fact that I tested it directly under the antenna isn't that big of a difference at comparing to the neighbors, because the radiation angle of the antenna already guarantees little RF in the neighbor's house, as well.

I'm a radio operator and a consumer electronics consumer, not a test lab with tons of test equipment. My point to all this is as follows: My test and yours that you're going to do is a purely subjective test at how much RFI we perceive is present. Your comments about a radio with -32db 2nd harmonic being a "TVI monger" are purely subjective with no technical measurement of what comprises a "monger". If TVI can be already be perceived and demonstrated with a stock radio, how much more TVI will be present with a radio with a -32db second harmonic is probably again subjective at those small of output levels. My simple, "poor man's" test is just fine at demonstrating real world characteristics, even though it is subjective too. We already know what the technical test will tell us because it was given to us using a spec analyzer: -32dB on the second harmonic. Everything else we're doing here is a mixture of conjecture and subjective comparisons, with many additional variables.

I have plenty of other appliances that generate a lot more RFI that are completely within specs (have you ever heard what a gas powered blower or a chainsaw can do to the neighbors AM radio? ) Heck, I can run 1 KW on 75 meters all night long in a well grounded, properly set up station and reboot my DSL modem every few minutes while talking. All the real HF equipment is perfectly within FCC specs, yet I can easily cause all kinds of RFI. I even managed to take out my own TV using DirecTV while talking on 2 meters. Why? Because of all the common mode current on the electrical wiring in the house, among other things. I realize that these are not examples of TXing on the fundamental channel 2 frequency and are also all fairly easily solved. The point is that the LAST thing I'm worried about is 32mW of output from a CB. And as Justin commented, what difference does it really make in the big picture if the average user of the CB is going to overmodulate it and run it into some dirty CB amp, anyway?

You know what the biggest RFI problem I have in my house is? When someone runs the vacuum cleaner while I'm trying to watch TV or use the radio. I hate that. Or the kids coming in screaming and yelling while I'm trying to make that rare DX contact. That interferes with MY radio and is annoying. Or when I run out of beer in the middle of a conversation on the radio and noone will bring me another. I get much more exited about those issues......

 

[C2]

The subjective argument is wholey understood, that was the point there. But there are real quantitative elements in our discussion, which are not subjective at all. Those elements are the numbers in our measurements.

As Justin said, the harmonic is 32dB down (-32dBc). This is a relative measurement, relative to 50W. The same is true with the -62 dBc that I report. Only, the spec is typically -55 dBc. The harmonic increase, as I pointed out previously, is on the order of 34dB when the carrier increase is on the order of 5dB. While you and I may not perceive this to be of any significance with our crude observations, but consumers at increasing radius' just might start seeing something they do not usually see. Do you think that TVI could be perceived more than one mile from your location, even though you did not notice any increase locally? Put it another way, a guy 20 miles away adds a 2-pill palomar to his stock radio, will you really perceive any difference in signal strength on your radio? No, you will not likely notice much at all.

Now, these comments by you and Justin:

"And as Justin commented, what difference does it really make in the big picture if the average user of the CB is going to overmodulate it and run it into some dirty CB amp, anyway?"

"what good does it do when a guy drives this radio into a 1 X 4 davemade, and overdrive overdrive, overdrive?"

And these points apply equally well to cut limiters and cap and resistor mods. So the point is that it does not matter at all.

 

[yama junk owna]

Back to the first question, now I have a question, would it not be cheaper to leave the radio stock and buy a small amp if all you are after is more power anyway?

2) Would that not work as well as an all out modded radio without all the splatter?

 

[Moleculo]

If it's a small cb amp that has transistors in a push-pull configuration, the second harmonic will perform about the same as the modded radio. The third harmonic on the cb amp (unless it's properly biased and filtered) will probably only be down about 18 to 20db. So is it more cost effective for the amp? perhaps. Which one is cleaner? depends on a lot of factors. But if you want a bit more power with no amp, then you have the option we've been discussing.

 

[C2]

If it's a small cb amp that has transistors in a push-pull configuration, the second harmonic will perform about the same as the modded radio. The third harmonic on the cb amp (unless it's properly biased and filtered) will probably only be down about 18 to 20db. So is it more cost effective for the amp? perhaps. Which one is cleaner? depends on a lot of factors. But if you want a bit more power with no amp, then you have the option we've been discussing.

probably no way, you would just as soon put in a stinger board if you want it in the radio.

Your talking about the third order intercept? Yes, typically the third harmonic comes up faster than the second harmonic, and with a push-pull configuration the even harmonics typically are not a problem because the phases are 180 apart and the harmonics cancel. But there is no way the third harmonic is going to be 20 dB down. If you run your amplifier correctly, all harmonics should still be under -55 dBc. If you want a little more power, put your money into a radio that has dual finals or uses a monolithic final.

 

[Roger Dodger]

Re: FCC

Not that your previous comment is even on topic, but I doubt sending it in to an FCC "LAB" is really a possibility. Most equipment is type accepted by sending in 3rd party tests, schematics and photos and proof of "good engineering" design.

You can go to this site:

https://gullfoss2.fcc.gov/prod/oet/cf/eas/reports/GenericSearch.cfm

and put in the FCC ID of just about any FCC 'approved' product and find the documents with which the manufacturer gained 'approval', or in the case of CB radios, 'type acceptance'.

Let's take a specific example:
The Motorola Talkabout T5820 Radio.
Find the FCC ID on the radio, which is AWWT5800
go to the site above
put in 'AWW' for the Grantee code
and 'T5800' for the Product Code
Click on Search
Pick either result and click on "DETAIL"
Say "OK" to the agreement that pops up.
Now examine the list of the 'OET EXHIBITS LIST'

NOTE the RADIO ITSELF is NOT sent in to the FCC for 'testing' or 'approval'. Only thing sent in is lab tests, schematics, photos, etc. And these tests, etc. are sent in via the manufacturer, importer or 3rd party test lab to "prove" that the unit in question meets FCC guidelines for the product.

Enjoy!

What? - not even on topic? Of course it's on topic. It was suggested that having a radio fully tested without any slant or bias as to it's true specs/performance or how to interpret them. Who but the FCC or an FCC referred testing lab could do such a thorough test? I know in reality that they aren't going to perform such a wish... but it was a hypothetical suggestion that would yield reliable data. I'm well aware of that link to the FCC id and of what its all about. I can assure you if you took a radio to an FCC tech, that he'd put it through the rigors to assure it was compliant. Bottom line here is compliancy.... not so much as how far out of whack it is. BTW, I'm a former factory trained Motorola tech, w/ FCC 1st Class Radiotelephone license and transmission site/head-end experience.

 

[949Jake]

justin could take an ad out in QST and the ARRL could review it and say it's great. :guitar

 

[Moleculo]

C2, have you looked at any cheap CB amps lately? Most have no bias, and no output filtering. I don't know what cheap amp you've looked at (maybe the old palomars and cobras?) but most I've looked at are closer to what I've stated.

 

[Roger Dodger]

justin could take an ad out in QST and the ARRL could review it and say it's great. :guitar

dunno if you're responding to my reply but if you are, the ARRL is far from what the FCC is. As a matter of fact, the ARRL is part lobby group, part R&D, and plenty of nerds. As for QST and the ARRL, they are bedfellows.

 

[freecell]

there are 2 "made-for-cb" amplifiers that i know of that do incorporate 5 pole LPF. you're right mole, the majority do not.

 

[ButtFuzz]

Good Grief

Another "no one but the government" can do it right automaton.

Also, I believe your post said FCC "LAB", not FCC "Tech" Since the government's dumbing down of the FCC requirements for both commercial radiotelephone permits and amatuer radio tickets, FCC "techs" are a dime a dozen.

A holder of an FCC Commercial Radiotelephone permit such as yourself does not mean you "work" for the FCC, nor does it make you an FCC authority. It only makes you licensed to perform work or testing or make transmissions according to the limits of your "license".

Also, your working for Motorola in a previous life gives you no authority. While Motorola equipment is, in my opinion, nice, much of the impulse purchase consumer stuff and cell phones are made for them by MAXON of Korea or the like. Just look at the FCC ID of the product, as I stated earlier, and it will lead you to the actual manufacturer of the item. If you are/were an expert technician on their commercial products, that is great. I hope you enjoy(ed) being on call 24/7 by your employer.

I am certainly not an expert in these matters, nor do I profess to be. However, I think you will find my statements true. You may or may not be happy with that, but there is no reason to puff yourself up over the matter.

I congratulate you on your 1st class commecial ticket.

"The amount of knowledge a person has on a subject is inversely proportional the the time he spends talking about it on the radio."

...or in this case, writing about it on a message board. Since I certainly don't want to be considered a blabbering ar$ehole, I will now discommence with this thread.

"Dollar bill, dollar bill, dollar bill. It's all about the Dollar Bill"

 

[949Jake]

justin could take an ad out in QST and the ARRL could review it and say it's great. :guitar

dunno if you're responding to my reply but if you are, the ARRL is far from what the FCC is. As a matter of fact, the ARRL is part lobby group, part R&D, and plenty of nerds. As for QST and the ARRL, they are bedfellows.

I was just making a smart @ssed comment, not really with you in mind, more with the ARRL and QST!

i just thought it would be funny, an 'export radio tech' with a ad in QST and the ARRL reviewing his 50 watt cobra and giving it 5 stars or whatever they do.

QST/ARRL knows how to keep advertisers, giving bad reviews is not one of these ways! :!:

 

[Butcher318]

I thought that was pretty good.