ICOM IC-78 HF SSB RADIO

[Cadence]

I've heard CB AM come in on TV audio and also come in on a CB turned off. The TV interference was 20 miles or so. I would think a skip may play hell with someone, or does not transmitting a carrier preclude that with SSB.

[stimpsonjcat]

Originally Posted by Cadence

I've heard CB AM come in on TV audio and also come in on a CB turned off. The TV interference was 20 miles or so. I would think a skip may play hell with someone, or does not transmitting a carrier preclude that with SSB.

If it was truly CB, that guy has an amp and the FCC will go after them if reported.

Or else he was VERY close the TV/CB.

Harmonics from the CB bands fall into the TV spectrum...this has been a war for decades. You can usually solve this issue with ferrites on your cable/antenna/power connections to the receiving TV/radio.

I once put up a very large dipole and the feedpoint ended up above the house. Worked great, but I could trip the alarm system mounted in the attic if I used too much power. I moved the antennas further away from the house.

[S/V Illusion]

Lots of misinformation being cited by seemingly well-intended folks but to put it in simple terms, using a ham radio on marine frequencies isn’t legal but it also isn’t the cause for interference usually.

Marine HF channels are spaced 3kHz apart. No ham radio I have ever tested exceeds that bandwidth under proper operating conditions nor does it produce spurious emissions that far off the center frequency. In fact, with the filtering flexibility inherent in contemporary ham transceivers (and not found in marine rigs) it’s possible to easily reduce receive bandwidth to 50hZ if one wanted. Whatever adjacent channel interference exists can be easily attenuated.

Let’s not lose sight of the fact most marine receivers lack any decent filtering and all lack the ability to adjust filter bandwidth to any useable degree. Therein lies a lot of the problem.

[Cadence]

Originally Posted by stimpsonjcat

If it was truly CB, that guy has an amp and the FCC will go after them if reported.

Or else he was VERY close the TV/CB.

Harmonics from the CB bands fall into the TV spectrum...this has been a war for decades. You can usually solve this issue with ferrites on your cable/antenna/power connections to the receiving TV/radio.

I once put up a very large dipole and the feedpoint ended up above the house. Worked great, but I could trip the alarm system mounted in the attic if I used too much power. I moved the antennas further away from the house.

CB SSB worked for me. No good buddies and had the range to tell the wife I would be late for supper 30mi out. I did enjoy some skip. Norway and Australia.
Even by chance recognized my father-in-laws voice 1500mi away with a little loaded antenna on my car.

[Hartleyg]

Originally Posted by stimpsonjcat

You set the DUT radio to min power, CW or FM mode, tune the SDR to see that freq, TX the DUT and note the magnitude.

Then Set the SDR to the 1st harmonic and do it again.

Check delta vs spec.

Now the splatter nature of the output is a little harder to evaluate, but when I did this test on the Baofeng HTs I had it was pretty hideous stuff.

Oh, dear. PLEASE try not to take this personally, but that method is highly unlikely to give you any useful information.


First, the Device Under Test (DUT) here is a 100 watt HF-SSB transceiver, and must be tested at it's designed power output. Your SDR receiver is VERY likely to let out ALL the magic smoke at a fraction of 100 watts. I looked up a couple inexpensive SDR receiver specs, and the absolute max input was generally +10 dBm (10 milliwatts), which corresponds to about .7 volts (at 50 ohms). Since the input amp is MOS, I would also expect that there are a couple of diodes protecting that input from static, so that's probably the reason for that limit.



Second, your SDR receiver is very likely NOT a good 50-ohm load for that transmitter, so all manner of things can happen with the transmitter when it is trying to feed a load impedance outside it's designed value.


Third, even if the input signal is reduced sufficiently, I think it is extremely unlikely that the SDR receiver front-end is perfectly linear across 60 or 70 dB of input signal, and this means that the non-linearities will show up as what appears to be harmonics as well as intermodulation (IM). As you know, the real input to an SDR receiver is an analog-to-digital converter, and making those things linear across any significant range is NOT trivial.



Note that NONE of these limitations apply to the intended function of an SDR receiver - but they will certainly be pertinent to trying to use it as a precision spectrum/signal analyzer.


I have no doubt your BaoFeng looked pretty lousy when examined this way - lets assume you dropped it to 100 mw output:
That means you were hitting the front end with perhaps 2.25 volts of RF. Both protection diodes were conducting heavily, changing the input quasi-sine waves into square waves and creating major energy at ALL the odd harmonics. These were also mixing with other signals such as the A-to-D sampling frequency and it's harmonics and anything else present in the system (non-linear junctions make EXCELLENT mixers) to create even more apparent spurious signals.


There is a reason lab-grade spectrum analyzers cost a LOT of money - and you still have to set them up properly to keep them within their limits!



Hartley
S/V Atsa

[stimpsonjcat]

Originally Posted by Cadence

CB SSB worked for me. No good buddies and had the range to tell the wife I would be late for supper 30mi out. I did enjoy some skip. Norway and Australia.
Even by chance recognized my father-in-laws voice 1500mi away with a little loaded antenna on my car.

Must have been back a ways or FLAT!

bands above 20m are crickets lately with no sun-spots.

[stimpsonjcat]

Originally Posted by Hartleyg

Oh, dear. PLEASE try not to take this personally, but that method is highly unlikely to give you any useful information.

<snippage>

There is a reason lab-grade spectrum analyzers cost a LOT of money - and you still have to set them up properly to keep them within their limits!

Hartley
S/V Atsa

I figured this would be the response.

So on the one hand, the ugliness of the signal is a MASSIVE problem, causing havoc the world around.

And on the other hand, the equipment needed to see said ugliness must be hyper-sensitive. A plain ole radio (like the ones allegedly being interfered with) is not capable of sensing the ugliness?

I ran the same test for several of my HF rigs using online SDR radios at various locations to see what the signals looked like.

Is it Sherwood tests? Nope, but if the radio is making a mess you'll see it.

[Hartleyg]

Originally Posted by stimpsonjcat

I figured this would be the response.

And on the other hand the equipment needed to see said ugliness must be hyper-sensitive.
.

No, you missed the point entirely - if your measurement apparatus is inventing the "ugliness" for itself because your testing protocol or equipment is lousy, you WON'T be seeing the truth. Sensitivity is NOT the problem here - linearity is, and cheap test equipment tends to NOT be linear.



Hartley
S/V Atsa

[ohgary]

Universial radio has them forsale rffun.com Cant ship to us address since they are export only.

[stimpsonjcat]

Originally Posted by Hartleyg

No, you missed the point entirely - if your measurement apparatus is inventing the "ugliness" for itself because your testing protocol or equipment is lousy, you WON'T be seeing the truth. Sensitivity is NOT the problem here - linearity is, and cheap test equipment tends to NOT be linear.



Hartley
S/V Atsa

I have no wish to fight you.

Your contention is that the cheap SDR is useless for evaluating radio performance because it might be non-linear? I will grant it is not ideal. IF it is even non-linear.

But if I counter that I tested multiple UHF/VHF radios locally and some performed waaay better or worse than others on the SDR display what would you say? Like an 857D was way farther down on harmonics and nothing outside the intended bandwidth vs the Baofengs. Is that just my junky test gear showing some brand preference?

I get it's not the best. Most folks don't own a Fluke 123B, I am betting you might. You can learn a lot from a blister-pack DMM. Same for the SDR.

[KP44]

The output does not match the specifications of single side band channels. They are sloppy, noisy, etc., and will incur the wrath of purests on this forum.

Purists? We have legal ships radio stations. We use the minimum power needed for our communications.
But most dirty radio operators seem to have have the uneducated opinion that more power will make their radio "blast through" all the interference. Thus it is LOUD and spills beyond the nominal bandwidth.

It is similar to having a loud party-boat in a crowded anchorage that lowers 2 PWCs that speed through the anchorage until 10 pm. Loud, dangerous, disrespectful, annoying; but not illegal enough in many areas to get official help.

Transmitting on any other frequencies is illegal unless you have a ham license, effectively at the General License level or above.

Amateur License is not difficult to pass. No code is needed, even for the highest license. You will learn a lot just by passing the exams.

[Brian.D]

Using a properly functioning HAM radio on Marine bands is like using your cell phone during takeoff and landing on an airplane. You are told it will interfere with the "planes navigation system" when in actuality tests have proven if does no such thing. They just don't want you to use it for safety reasons.

Basically the same is true with the HAM radio. Manufactures of Marine radios spend large amounts of money to meet the standards and they want that money back. They have a market for that Marine radio in the commercial shipping industry. Why push that down to us the casual sailor/boater?

As mentioned above, no doubt newer HAM radios are probably tighter in specs than older Marine radios whose components are deteriorating and going out of specs.

This is JMHO and not based on any testing or empirical data.

[GrowleyMonster]

So what is the big deal with simply buying a type accepted marine HF SSB radio? M802 costs less than a lot of high end HAM or SWL rigs. M700PRO is available on the used market for well under $1k. Both can be used on the HAM bands as well as Marine channels. Add an ATU and you are still in the game pretty cheap.

[Brian.D]

The Marine radio cannot do 1/8th of what a "high end" amateur radio can do at the same price cap. Apples and oranges. Marine radios are basically "dumb" radios with really tight circuitry. An equivalent new "dumb" amateur radio is maybe 1/4 the cost of a new "dumb" marine radio. However, this is not a good enough radio to negate getting a legal radio for Marine use.

There is the assumption that if one has only an amateur radio on their boat that they are using it on Marine bands. If the FCC wanted to tag you for that then you will lose in a court of law unless you can prove that you never transmitted on any Marine frequency. Good luck.

Again, JMHO

[KP44]

Originally Posted by Brian.D

As mentioned above, no doubt newer HAM radios are probably tighter in specs than older Marine radios whose components are deteriorating and going out of specs.

This is JMHO and not based on any testing or empirical data.

A lot of uneducated opinions abound. Thanks for pointing out that this was your observation and speculation.