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Crystal two-way radios vs modern walkie talkie.

13K views 26 replies 14 participants last post by  Outpost75 
#1 ·
I got a pair of MacDonald CE-420 2 watt, 3 channel walkie talkies. There is only a single set of crystals in them- channel 11 (27.085 Mhz). Haven't tried them yet. But I was wondering if they are decent vs modern technology? I don't have a radio operators license>

Does anyone know how they compare with the ones from Motorola, Midland, or Baofeng and the like? Are they worth getting more crystals for?
 
#4 ·
The good thing(if they work) is that they're likely to last a very, very long time.

The bad thing is that it's only one frequency(and it's sidebands) and that because it's in 11M, an efficient antenna for it will have to be much, much longer.

If you're just looking for a simple plug n play type set, modern midland or cobra CB HTs are much better.
 
#6 ·
I suggest getting a license as its not so important about the license if things go south but the skills and knowledge you learn in order to get the license. Its not that hard for the Tech license also it gives you a whole perspective on how the radios will work by "Transmitting" as just listening does not tell you a whole lot on your set up and situation and location when you need to transmit. Its a mere 15.00 bucks and you will be leaps and bounds over others just taking a the time to get that license to operate and practice etc.. Also this really depends on what you're needs are and what you are trying to do. The baofengs are cheap alternatives but as far as them holding up like your radios there is no comparison. The beofangs are chinese and cheap need I say more. They are cheap to buy and use and practice on but would I depend on them to have as my survival needs when the SHTF? no... That said CB's are not what most want here. The other thing is Midlands are not what you want either... Those are the worst as they limit power to 1 measly watt and then advertise GMRS which is like putting a 4 cylinder engine in a Lamburgini body whats the point? with GMRS you should be able to use up to 5 watts with a license. The reason those over hyped Midlands are sold to so many is because its only 1 watt because you have to have a GMRS license and most people do not have them. Sot they skirt around the whole license thing by limiting the power of Midland radios and also making the antennas un changeable.. So basically you are using a silly FRS radio which in that case save your money and buy the cheap Motorola FRS 1/2 watt limited radios. Or go with those Chinese models to play with and use but buy one or two good Yaesu's or Kenwoods or ICOM HT handsets. Then get a decent portable antenna you can use with that quality HT handset. You will be leaps and bounds over some silly kids toy midlands. To many any decent person trying to prep should get a Tech license and know the simple basics its not that hard or expensive to do. It will only take the average guy a couple of evenings of studying and a couple of hours on a saturday to take the test. The knowledge you gain will serve you very well.
 
#7 ·
You don't need a license for those radios (the ones you already have), they operate in the CB band.

They will NOT compare well to the other radios you mention. Those radios are on completely different bands than your CE-420's, and different bands act differently.

As someone else mentioned, the antenna is related to the band (the band is a range of frequencies the radio works in), and in general antennas for that band are pretty large. But on hand held radios like that they try to make them small, and that means an inefficient antenna. While on the other radios you mention the bands require smaller antennas, so they can be more efficient while still being OK for hand held use.

Power. Your radios are 2 Watt radios, and I bet they don't put out quite 2 Watts. The other radios you mention are typically more like 5 Watt. So even if they were all on the same band the other radios would have an advantage. And they are not on the same band, the advantage of the other radios is multiplied by their operating bands. VHF and UHF (the bands those other radios work in) are simply more dependable for local communications than HF (the band your radio works in).

Mode of operation. Your radio uses AM mode. AM is fine, but FM (the mode used by those other radios) is better for dependable local communications.

You already have those radios, try them out and see if they do what you want. But to answer your question, no, they do not compare well with the other radios you mentioned.

T!
 
#8 ·
I think its interesting you can take the crystals and reverse them and you are then elsewhere... (I assume this would work with ANY 2 crystals of any frequency but you might not wanna try it on any VHF band because you dont know where you might end up! (If you are below 136 it would not be good! (Thats protected band (108-135.975))

Any other protected band spaces?? (Besides the air band)
 
#9 ·
I think its interesting you can take the crystals and reverse them and you are then elsewhere... (I assume this would work with ANY 2 crystals of any frequency but you might not wanna try it on any VHF band because you dont know where you might end up! (If you are below 136 it would not be good! (Thats protected band (108-135.975))
Not sure what you are trying to say here, crystals are not polarized, there is no right way to plug them in. Take a crystal out, reverse it, flip it around, and you are on the same frequency as when you first started.

T!
 
#11 ·
He said "I think its interesting you can take the crystals and reverse them and you are then elsewhere... I assume this would work with ANY 2 crystals of any frequency"

I don't read what he said that way, but giving the benefit of the doubt...

The radios being discussed in this thread are 3 channel crystal controlled radios, each with one set of TX / RX crystals in them. Are you saying you can swap the TX and RX crystals in these radios, put the TX in the RX slot and the RX in the TX slot, and it will work, and now you will be on a non-standard CB frequency?

T!
 
#15 ·
Try it...
I have, generally the only way this works is when the radios (and then some radios only, not all) are very close together or the signals are very strong, then you get IF image issues going on, and can hear the other station. But often reduced in strength, sometimes by 30 dB or more.

(edit for clarity) What you are describing is possible with poorly designed radios, as they may suffer from poor image rejection. So it is very dependent on the specific radio. Very early or very inexpensive radios are more likely to show this. A well designed radio with some thought in RF bandpass or tracking on the front end will not do this or if it does will show great attenuation of the signal.

You are thinking about this way too much
No, I am not. What I described is basic superhetrodyne radio 101.

The is nothing digital about this fine, solid state piece of gear.

The two crystal frequencies are the 455 shift
Not sure what you are saying there, the description I wrote was of a totally none digital format. In fact, the architecture was taken from my Johnson Messenger 2, I looked the schematics over before I responded, just in case I was thinking about it wrong. And then I swapped the crystals in the Messenger, just to prove to myself I knew what was happening. This is not the first time I have messed with crystals in CBs, I did a lot of experimenting with these kinds of things in the early 70's, mostly for my own understanding.

What I described was the two crystals having a 455 kHz shift. The reason the RX crystal is shifted 455 kHz is to match the IF of the receiver.

But lets say I might be wrong and it works the way you say. I know I am not (outside the possibility of an IF image reception), but lets discuss the possibility anyway, shed some light here.

I have to ask two questions, if you can answer them then you go a long way towards supporting your contention, and I will have to eat crow.

The crystals are cut about 455kHz apart so if you swap the crystals TX to RX, you will now be transmitting on the old RX Freq and receiving on the old TX Freq.

Example: Channel 10 uses 2 crystals:
Channel 10 Transmit:27.075 MHz
Channel 10 Receive is 26.620 MHz

That means the Radio Transmits on 27.075 MHz, but Receives on 26.620 MHz.

My first question is, do you believe what you said here, that a normal CB radio, when properly configured for channel 10 operation, transmits on 27.075 MHz and receives on 26.620 MHz?

My second question is, if the above is true, and a CB on channel 10 transmits on 27.075 MHz and receives on 26.620 MHz, how do two radios so configured talk to each other? Radio A and B, both tuned to channel 10 A transmits to B on 27.075 MHz, but B is receiving on 26.620 MHz, so B never hears the A transmission.

It could work, operating split like that, if the two radios were inverted from each other. A transmitted on 27.075 MHz and received on 26.620 MHz, while B transmitted on 26.620 MHz and received on 27.075 MHz. But that is not what is happening here if all normal channel 10 operation is 27.025 MHz transmit and 26.620 MHz receive.

Answer those two questions, the first is a simple yes/no, the second may take more description, and maybe I can understand where you are coming from.

T!
 
#16 ·
First Token is correct on this. When a radio transmits on one frequency and receives on another, it is called duplex operation. CB radios do NOT operate duplex. There wouldn't be any reason for it.
In the HAM world, duplex is used for local repeaters so that individual radios do not interfere with the "repeated" signal. It is also used in some contesting to avoid pileups on the frequency where CQ is being transmitted and on some occasions when you are trying to communicate with someone in a different country where the allowed transmit frequencies are not the same as your own.
 
#18 ·
Sorry to waste bandwidth
Don't be sorry Rev. I owe you an apology if I gave the impression that your input isn't wanted.

It isn't a waste of bandwidth if we are learning. I wasn't aware that crystal controlled CB radios generated their IF frequency with a different crystal. I just got through looking into it and I have learned something new.

Some of the biggest advances in science have been due to errors.
 
#19 ·
FirstToken said:
I have, generally the only way this works is when the radios (and then some radios only, not all) are very close together or the signals are very strong, then you get IF image issues going on, and can hear the other station. But often reduced in strength, sometimes by 30 dB or more.
Well I would imagine it depends on the antenna on your radio.... That much lower freq would cause your match to go sky high and yes your output would be reduced most likely.....
 
#20 ·
I have, generally the only way this works is when the radios (and then some radios only, not all) are very close together or the signals are very strong, then you get IF image issues going on, and can hear the other station. But often reduced in strength, sometimes by 30 dB or more.
Well I would imagine it depends on the antenna on your radio.... That much lower freq would cause your match to go sky high and yes your output would be reduced most likely.....
You left out my edit (the next paragraph) that went into a little more detail:
(edit for clarity) What you are describing is possible with poorly designed radios, as they may suffer from poor image rejection. So it is very dependent on the specific radio. Very early or very inexpensive radios are more likely to show this. A well designed radio with some thought in RF bandpass or tracking on the front end will not do this or if it does will show great attenuation of the signal.
As for antenna and antenna match, older radios like what are being discussed tend to be more robust when it comes to SWR mismatch than anything made in the last 40 years. Many, probably most, of these older radios have no automatic fold back if the SWR is too high. So high SWR or not, they try to make as much power as they are adjusted for on that particular frequency. Of course there is some reduction in power caused by multiple issues. The reflected power (or return loss), obviously, but you have to get up to 6:1 SWR before half the power is returned. Antenna inefficiencies, how little of the power put to the antenna actually gets radiated into free space, of course will be a factor.

But the big factor I was talking about is the design of the receiver front end, the bandpass filter and how it works.

A radio tuned to channel 1, with a set of TX and RX crystals as described and a 455 kHz IF, would have a TX and RX frequency of 26.965 MHz. The TX crystal would be on 26.965 MHz, but the RX crystal would be on 26.51 MHz. The RX crystal is cut to 455 kHz below the desired receive freq, and the IF is added to the RX crystal controlled oscillator.

The other issue, and the thing that the technique Reverend Bow was talking about leveraging, is the fact that the receiver also has the potential to receive a second frequency, which is the RX crystal freq minus the IF, instead of plus the IF as intended. This would tune the receiver to a second freq at the same time as the first, in this case the 26.51 MHz crystal freq minus the 455 kHz IF, making 26.055 MHz.

Receiving a second frequency when you mean to receive only one can be a problem. So the designers put in a bandpass filter (BPF), sometimes only a high pass filter (HPF). I will only talk about a BPF, but an HPF would have the same issues. The exact design and adjustment of this filter will determine the fc (cutoff frequency, or the "edge" of the filter, below which it will try to block signals from being received) and how steep the filter skirts are (how closely, in frequency, they knock down signals outside the desired frequency range).

Since we are talking about 23 channel CBs here (you almost never find a 40 channel CB with RX and TX crystals for a given freq, they used other techniques even when crystal controlled) it was pretty simple to determine what the fc of the BPF should be for a good design. Channel 23 is 27.255 MHz. Minus the 455 kHz IF leaves 26.8 MHz, this would be the RX crystal freq. And so the IF image would be on 26.8 MHz minus 455 kHz, or 26.345 MHz. The basic scheme of the radio would be trying to receive both 26.345 and 27.255 MHz.

If the designer wanted to make sure the radio would only receive the desired frequency, and not the undesired IF image, he would put in a BPF that had an fc above the highest image freq (26.345 MHz) and below the lowest intended freq (26.965, channel 1). Steep skirted filters are more expensive to make then shallow skirted filters, so to save cost you push the fc up to as close to channel 1 as you can, often around 26.8 or so MHz.

This means that frequencies below the fc of the filter, for example the 26.8 MHz number I used, will be attenuated, the filter blocks them.

Receivers that have a well designed BPF will not do what Reverend Bow was talking about, you can't just flip the crystals around and be using a lower frequency, out of the normal CB band. But receivers that do not have a well designed bandpass filter, or have an fc below 26.5 MHz, or if you go into the radio and make a minor tweak to the BPF, will do what he has described.

Of course then you will be receiving two frequencies, both the + and - IF. For channel 1, if you flipped the RX and TX crystals, you would be transmitting on 26.51 MHz, and the radio oscillator and IF system would be trying to receive both 26.51 and 27.42 MHz (LO-IF and LO+IF) , at the same time. With a properly designed BPF the 26.51 MHz signal would be greatly attenuated. But if the fc of the BPF is below 26.51 MHz, then it will work fine.

If the designer does his job this flipping crystals technique will not work, but if he did not, or was cutting cost, it may work.

This is one of the reasons freebanding or outbanding on the upper ferqs (above channel 23 and later 40) was more popular than doing so on the lower freqs, there were more radios that would do it across wider ranges with a simple crystal swap. On the receiver side there was little or no reason to actually use a BPF, an HPF was really all that was needed. And an HPF is cheaper to build than a BPF. So the receivers tended to work well for a long ways above the legal channels. The transmitters did require a low pass filter (LPF) so they would not interfere with TV stations on the 2nd harmonic. But again, it was cheaper to build an LPF than a BPF, so a typical CB radio would contain, in the RF path, an HPF with an fc someplace below channel 1, and an LPF with an fc around 30 MHz and with not great skirts. This was a much lower cost option than building a single BPF to do both jobs, and still did things well.

T!
 
#22 · (Edited)
There are good reasons crystal radios are no longer made, and the 1st one is that your portable radio is just one drop from disaster.

Since crystals aren't so popular anymore, a lot of the manufacturers went away. Those that are still around are more into entire TCXO's now, so IF you can find someone to make you a crystal, it will likely be of poor quality and not properly aged, making it susceptible to frequency drift and secondary resonances that may cause birdies right in the 1st oscillator stage.

Also, the manufacturer needs certain temp compensation information regarding your radio's design which may not be available anymore.

Get a modern frequency synthesized radio. They still use crystals, but they are of much smaller mass and are far more rugged than older styles. Ceramic filters and line strips have replaced a lot of what used to be done by the crystals, and because they can be tuned by the microprocessor have better dynamic tuning range, sensitivity, and image/adjacent channel rejection than the old stuff.
 
#23 ·
Crystals

years ago, many in fact...

I use to do a split. I would take a receive crystal and use it for transmit. Since U R shifting 0.455 mhz downward, starting with a higher frequency/channel will keep U close. This is important because some radios have a relative narrowband capability.

This was also cost effective, I would only have to buy one special cut crystal, from Jan Crystals , IIRC they were out of Florida.

For example Ch 40 is 27.405 minus .455 =26.950 This just slightly below channel 1@ 26.965 So your antenna and "front end" are still within range. Another advantage is the frequency has a different spacing. .950 where CB frequencies end with a 0.005 mhz.

The truth is.... This is obsolete. Long antenna, low power output, AM modulation, bulky radio. Seriously, one can buy a Baofeng about as cheap as a good set of batteries for that old radio. That radio probably takes 8 if not 10 AA batteries.
 
#24 ·
FirstToken said:
As for antenna and antenna match, older radios like what are being discussed tend to be more robust when it comes to SWR mismatch than anything made in the last 40 years.
Oh yeah I know!!

In the 80s I had a realistic TRC 422 and that thing got SO HOT you could cook eggs on the back!!! (But it stayed on freq..... Quite a good AM radio)

I remember one time hooking up a TV antenna when I was @ my friends house and talking around the world!!!!!! (The match was sky high)
 
#25 ·
My first radio was an ICOM 2AT with the thumb wheels on the top for changing frewuencies. Biggest problem was it didn't have the PL Tone switches in it so I got my radio club mentor and he put an 8 pin dip switch in the back of the radio so I could switch to the correct PL Tone for whatever repeater I was trying to connect to.

I've still got that rig.
 
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