galaxy cb

dbm not DBM. Into what impedance? Your question is posed poorly with far too many unknowns for a quantitative answer. I assume you know that so I am unsure what you are really trying to ask. Measured under what conditions with what equipment, at what temperature? Inside a Tempest shielded Faraday cage or just sitting on the bench at room temperature hooked to a 1200 Super S? Or are you wishing to negate this and consider the noise floor solely in terms of internal Johnson-Nyquist and Shot (quantum) noise? I surmise you are asking with AM in mind you did not specify that either. Simply too many variables such as extraneous noise sources, localized sources, as well as even the level of solar activity and cosmic radiation flux would need to be specified, so would the distance to the nearest thunderstorm activity as well as it's intensity. If I try to make an educated guess as to what you are trying to ask all I can say is you know as well as I that these radios can be easily adjusted to hear -120 dbm (decibels per milliwatt) into 50 ohms, or around 0.33 microvolt; so the floor is below this; but we both know the manufacturers spec a half microvolt at 50 ohms on AM for the reasons mentioned in my previous post. i.e., these things are designed and constructed sloppily using cheap components. In short pretty noisy compared to say my old Johnson radios. Still overall not bad radios for average operating conditions and the price is decent for the communicating you can do with them. I love my 2950's and 70's but I still wish the computer and entire synthesizer sections were in sealed compartments.

 

HUMMMM .....

Looks like you have MILLIONS in test gear at your place .....

You know dang well what I am asking so why the smart answer .... ?

dbm/DBM HOWEVER you want to use it is ALWAYS into 50 ohms for RADIOS maybe on PHONES you might find 450 or 600 ohms.....

I have on my bench a IFR1200-S nice works just fine for the 1500 radios I am PAID to mantain at work and a OLD lampkin here in the shack goes to 990 mhz and down to .1 UV MORE that good enough for a HAM or even a CB shack .....


EVEN when I worked for Sperry engineering ( microwave ) or St. Pete PD shop on the trunking system we had little use for a screen room and that was so we did not interfer with the system while testing .....

Since noise at CB is well above -120 DBM / dbm whatever ..... I take you answer to be you think the older radios had less internal noise and you like them better ...... They took the time to shield things and had less LO noise .....

Right now on 144 mhz with my new mast mounted preamp ( 20 db gain @ .5 db noise ) so that i don't have to add 2DB coax loss to my system noise figure feeding a TS-2000 @ 50 HZ bandwidth I can just hear the stronger EME stations using my M2 9 elm antenna .... not to shabby ....

 

"I take you answer to be you think the older radios had less internal noise and you like them better ...... They took the time to shield things and had less LO noise ."

My point exactly. It was not that much more expensive to use subsection shielding so why did they refuse to even try to market one. All I wanted was the performance of my Viking with the features of my RCI.

This was the very project Bill Good was working on but He died before it was ever completed. He spent hours on the phone talking over ideas in His last few months. I think if he had not been having so much trouble with the Comb filtering idea for the LO's He might have finished a prototype. We both agreed however that it would end up being too costly to market. Likely would have had the same fate as the ARF line. Few in the 70's could afford a few grand to buy a CB. Would have been nice to have one though.

 

The problem is just like on VHF/UHF you hit a point that nothing you do will be seen by the end user .....

MYSELF ... I love DSP and don't see why is is not much more common in CB radios .... it can be built into one chip and if you look at what it can do for noise reduction bandwidth control except for cost on mid range CB radios it should be standard on.

10 and 6 meters have high background noise a well adjusted DSP filter does wonders when you are trying to hear someone down into that noise.
Radio Shack made a CB DSP filter I have several of them They WORK however they are audio not RF/IF so they are limited you can't adjust bandwidth or null out a station like IF will allow you to do.

AGAIN much is limited by COST and the fact that the CB market is a limited one .

I only have my FT-840 left that does not have DSP and it is mainly used for FM/AM on 10 meters .... IF I can find anyone on AM FM is not a problem 29.600 is quite active.

 

I played with the Radio Shack one back in it's day but I did not care for it's performance as I seldom did CW and even for SSB I was not happy with it. I even played with the 70C20 when TI came out with it but I never could get good at writing code. Just no patience for the endless programming of a zillion lines for even simple subroutines. I think I would rather have a lobotomy than write a complete program. Just running the LCD display takes forever to code. Around once each decade I think to myself if I had only started practicing back then I would be good at it by now. I agree though DSP would be cheap to implement in a CB today. Why would Cobra build that crappy Sound Tracker when they by now could have come up with a nice DSP on a fairly small circuit board.

 

The Radio Shack is audio ... just like the IC-706 and IC-718 ..... it works but not as well as IF/RF
The TS-2000 is the oldest radio with TRUE IF DSP still being made and the new radios kick tail when you put one against it .. I'm looking at a ft-950 and running it with a Transverter on VHF.

ONE chip DSP for a CB no problem .....

 

"The Radio Shack is audio"

Again I don't see your point. I know it is audio, I owned several of them years ago. But their ability to reduce noise sucked on SSB and AM was too wide for them to be of use. I did not care for the quality of sound after it went through them. To be honest a tone control sounded better. Yes back in the old days I tried EQ devices meant for your stereo on the receive audio, and a 5 band EQ actually worked better for me on SSB than the DSP-40 Active Filter. If you ever played building opamp active filters you noticed the effect I am trying to describe when the Q was too high. The audio gets a hollow sound which had a little too much ring when you went too narrow. It was OK for CW but as I said I did not like the sound quality on SSB. The old Yaesu 101's which had the RF processor board did fairly well, the board mounted on top the VFO unit. Very rare however. You are right the IF is the only way to go, this is where I first started playing with comb filtering. Sony or someone came out with it for working on chroma signals, and reading about it got me to wondering about it's use for SSB, and maybe even AM.

 

When DSP is done in the IF you will see what i'm talking about ..... You can shape bandwidth notch out signals and noise ....

I have built op-amp filters back 40 years ago you can and do get a ringing sound .. again my TS-2000 is very old but once you have DSP in your radio you will see why almost all radios are going that way.

Another intresting filter is a SCAF I have one very good at killing background ...

http://www.idiompress.com/scaf-1.php

 

"EVEN when I worked for Sperry engineering"

Forgot you mentioned that. 40 years ago I worked at Sperry Flight Systems at 19th ave. R&D location in Phoenix. I liked taking my lunch break under the wings on the first AWAC while it was being built as an experimental prototype. Nice sun block and you could sit outside having a smoke. Always wondered how that thing flew with about a zillion miles of copper wire in it, must have been real heavy. Anyway I got to experimenting with real high quality instrumentation opamps which were still new devices to the electronics world at the time. IIRC it was 67 when the first UA709's came available to buy though expensive. There was a director named Ron Crowe who pestered me to design a new audio filter for a movie He was working on. He had one scene in a movie He was making that was impossible to record. The camera was setup across the street from a couple walking down the sidewalk in downtown Phoenix. The effect He wanted was picking up their voices perfectly clear as if you were hearing them from the camera location. What I built was an EQ combined with an inverse EQ function using three dozen opamps. What I wanted was extreme precision in notching out certain frequencies while increasing others. Meaning very narrow bandwidth notches (and boosts) which were adjustable on the fly as traffic sounds varied. My box had a large number of knobs to turn while you listened to the couple talking which was attached to a parabolic dish/mike setup I built as part of the whole system. Worked so well it was scarey, as long as no Fred Hurley trucks were going by. Those newspaper haulers had sounds right in the perfect range for voice. Took a long time to build as you could not find so many resistors of just the right values and perfectly matched. I spent many hours taking values just under and using a triangular file cutting a notch in each one until the ohms were exactly what I needed, then sealing the cut with polystyrene Q dope. A long process but it worked to perfection. I don't know if the movie was a good one as I never saw it meaning most likely it flopped bad but that scene was surely unique. Come to think of it I never heard from Crowe again either so I imagine he lost some big bucks for someone as I do not recall seeing any movies after with His name in the credits. Maybe He went into some other line of business. Thinking about how many hours I worked designing and building that thing makes me wish DSP and comb filtering had existed back then.

 

Sperry Microwave in Clearwater Florida exsisted from the mid 70's to the late 80's. I worked in RF R&D from 1980-1984 when they shut down 90% of the shop. Most of what we did was 96 GHZ ( 96,000 Mhz ) microwave development. My job was to build test and work on any assembly that went with it ... Yep got to work with some REAL neat toys ......

Before that I worked at C-Ran on UHF down flyer ( 243 Mhz ) radios and after that E-Systems engeering on the WSC-3 and ARC-182 radios ( 200-400 Mhz ) radio systems .
I left in 1991 when that program was winding down and the CMD Div. was shutting down

I then went to public safety working for a local PD in their shop and on to the jail .... which I will retire from in 3 years ....


Photo working for sperry engeering at the Kennedy Space Center in 1982 Pad 39B you can see a shuttle being rolled out to pad 39A in background ... like I said I got to work with neat toys ...
Im on the right