Oil cooled antenna

Instead of a bunch of squealing it will be like sitting in a room full of people talking at the same time.

 

I hope you're right and that he's able to get my 98 working that well. I'm actually kind of looking forward to being the guy who is "talking to himself", and telling stock radios owners how far they are really getting out. I'll be spreading the word/education.

 

I am losing your point here.

Noise floor isn't important when you look at the performance metrics of any receiver.

I've got a drake with better noise floor but it receives poorly because the rest of the system within the radio. I've also got a Collins that has issues but its noise floor is as good as my new radio, which that radio is actually the best you can get right now.

So what if there are 8 CB techs that can do this or that to improve one aspect of a radio, it doesn't mean there are NOT others out there that know more or do more without the accolades given to them by a small amount of people who solely depend on them.

By the way, just to set the record straight, I call the guy who works on stuff for me 'my tech' because it is easier than to say this engineer guy who runs a repair shop for military and satellite equipment. He does my overflow work and stuff I don't feel comfortable with, like my R&S receivers. He mostly works on the stuff I don't feel comfortable with but if I send him a CB or two, I get a call with him always saying "are you crazy?". He still does the work but thinks it is a joke. My point is this - I do not depend on him for things I do myself.

There are only a couple that matter, the noise floor for any radio is a rudimentary number, but there are a few others that show the possibilities of the receive system in the radio.

Not trying to deflect your response but you need to see where I'm coming from so I'll give you a hint - Sherwood

It doesn't look like that, however it was the first marketed open coil antenna for trucks.

That's pretty interesting

 

I'm assuming you're referring to AGC threshold

 

I agree that noise floor is not the end-all-be-all, but I disagree that it is unimportant. I hate white noise, and I hate using squelch, so I want the noise floor to be as low as humanly possible.

But, I don't want all the concentration to be on that.

 

Nope ...But that is another test that should be done.

I am going to explain this in simple terms from memory.So please if I make a mistake, I am very tired and not focused on much this morning - third cup of coffee with espresso isn't working.

A more important test is the 'Third-Order Dynamic Range'.

IN the case of CBs, it is a wide dynamic range test that is needed.

It is a measurement of how the receiver handles both weak and strong signals at the same time.

The higher the reading, the better the receive.

There are generally two versions of the test, a narrow and a wide. The narrow is usually done with three generators, one set at the center frequency, the other two set at 2khz off center.

The wide is set at 20 khz off center.

In the case of CBs, they can be 20 or like my guy does sets it at 10.

Many CBs, well most of them fail to achieve anything better than 35db. Only a couple that been produced have anything achieving more than 50db and those are not produced any more (actually for more than 3 decades).

One of the best is the Johnson 123A, a very good design, departs from the norm and has better than 50db DR.

Yeah you can laugh about the 123A but that's the truth, it is a good design, only made because someone at Johnson looked around and saw a problem so it went into production. If someone says X export or some other superduper radio is better, they don't know what they are talking about.

But to show you what I mean let's compare these numbers of what ham I own and the results of the testing I've done (a caveat I have to point out is I have other stuff that exceeds the quality of the ham stuff by miles - my spook radios are one such group).

My drake R4-b (refurbished by Drake tested out of the box) is at 53db

My FT101 is at 69db

Collins 75a4 and r390 both sit near 60db

My SDR radios are all above 75db with one measured at 105db.

The reason for the SDRs being an improvement is the fact that they take the signal and put it through a math process to pull out the signal, they can be a broad band (DDC) front end and do wonders with the computer. I am looking at building one in the near term with a very narrow front end (the design is called a μtune front end) to improve weak signal reception.

These radios represent the low noise figure bunch, that is average for good equipment - 130 dbm. I've got others (many) that have a higher noise floor but I won't bother to give that data.

Noise floor is part of that measurement and the truth is it means little in the cb band no matter what people want to believe.

One reason is these are mostly mobile applications we are talking about, there is no right mobile application that can recreate the what a 'base' can do. What I mean has to do with the relationship between the RF and earth ground, and that leads me to the the other part of it, the RF BAND NOISE supersedes any benefit of having a low noise floor, because of the lack of an earth ground.

What many think as quiet isn't, there is all kinds of noise (more tests) floating around, mixer noise, phase noise from the synthesizer and so on. then you have band noise and other noises produced outside the system like static from other cars. What I see is it comes down to trying to achieve FM quality receive but you can't achieve FM quality quietness with AM radios so the sales pitch is normally off the mark by miles.

One thing I have not seen anywhere but among a few in my areas is taking a CB and adding a synchronous detection in the receive chain, talk about a good thing. My little TRC-452 radio has one installed, what an improvement it has made with weak signals. BUT then again it also has a modified front end too.

So that said, another issues or really the real problem is with a design that goes back to something like 1965, and had not been changed since in not only your common radios but those high end junk exports people buy. A few, not much but just a few have departed from this design to try to get a jump on their competitors but failed for one or another reason. The worse of the worst is these 10 meter export radios with broad front ends and crappy selectivity, they are really bad. BUT that's another couple of tests that could be done.

OH and I've got to comment on how these noise floor tests are done, many times I've seen "top techs" (not going to mention names) doctor the tests up because they don't either; use the right equipment or set the test up right. Just because someone has a top end test equipment (not the IRF surplus stuff but $10k stuff) doesn't mean they know how to use it right or worse yet the thing hasn't been calibrated in a long long time.

I hope that answers your question.

 

Well written and I learned something. Thanks Ridgeline.

 

Spesking of which, I keep seeing the term "-135 dB" bandied about. Since I'm somewhat of a purist (read: anal) about apllied physics, is this strictly a recurring typo for "-135dBm", which shows an absolute value compared to a known value? I ask because the phrase "-135 dB" implies simply a ratio lower value than *something* that should be listed as "-lower than".
I certainly don't mean to disparage any of the posters here; most of y'all are smarter than I am
Toodles & 73

 

Point taken but to those who don't understand what he said, the correct usage for noise floor is dBm while dynamic range and other tests are dB. I don't always type in the right things, like when talking about resistance, I could use Ω but say ohms.