Sideband CB (27MHZ) Radios Making a Comeback - Cheap Long Distance Comms

[Gav110]

G'day.

I was browsing ebay looking at Icom and GME UHF radios when I cam across a guy selling a Cobra 148 GTL AM/SSB 27MHZ radio.

NEW COBRA 148 GTL AM/SSB 40 CHAN CB RADIO 27MHz 148GTL - eBay CB Radios, CB Radio, Radio Equipment, Electronics. (end time 17-Feb-10 12:24:23 AEDST) (http://cgi.ebay.com.au/NEW-COBRA-148-GTL-AM-SSB-40-CHAN-CB-RADIO-27MHz-148GTL_W0QQitemZ200429570107QQcmdZViewItemQQptZAU_ Electronics_Radio_Equipment?hash=item2eaa88883b)

The mere mention of the name took me back 'when I were a lad' to when I had an old Cobra CB and 1/4 wave antenna in Perth. On days with the right weather conditions, I could speak clearly with guys in QLD, VIC and NSW (using the principle of 'skip' where the signal carries and bounces through the atmosphere assisted by certain cloud formations).

Apologies if I am off on the technical details - am not an expert - this is my general understanding from personal experience.

'Real' CB was king then, before UHF seemed to creep up and take over - ostensibly because of its clearer and simpler operation, albeit over shorter distances.

27MHZ definitely has more 'tuning' required, with SWR, squelch and other odd sounding names, but my understanding is that once tuned with the antenna and well installed, there are few issues (and thousands of truckers still use it). These newer sets also seem to have more ease of use functions.

These radios have in most cases, 3 'bands' - AM, Upper Side Band (USB ) and Lower Side Band (LSB ) - together, Single Side Band (SSB ) AM transmits at a regulated 4 watts (so what? UHF is 5 right?), but here's where it gets interesting - SSB transmits at a legal and regulated 12 watts :eek:.

The benefit is obvious for our style of use - in clear atmospheric conditions, ranges of 50-100 KM are common, and where the cloud conditions are right and create enough skip, you're reaching people all round the country - in a mobile, whip antenna set-up.

A lot of owners add a 'home base' unit (same spec), and either another whip or a proper base mount antenna (.664 wave or similar) and with a decent power supply - such as the set-up below - have awesome TX/RX power, with possible global pickup with the right set-up and conditions:

ULTIMATE DELUXE CB RADIO HOME BASE PACKAGE GALAXY DX959 - eBay CB Radios, CB Radio, Radio Equipment, Electronics. (end time 07-Mar-10 16:15:05 AEDST) (http://cgi.ebay.com.au/ULTIMATE-DELUXE-CB-RADIO-HOME-BASE-PACKAGE-GALAXY-DX959_W0QQitemZ200415316005QQcmdZViewItemQQptZAU_E lectronics_Radio_Equipment?hash=item2ea9af0825)

And here's the best bit: no license required, no ongoing fees (like HF and satphone) and the purchase cost is equal to or lower than UHF.

The Cobra above which is one of the best on the market (the 148 GTL has been the truckers favorite for 30 years, and the Galaxy is the purist's favorite) - and you can buy the main unit for under $300 new on ebay. The only other thing you need is a whip antenna and possibly a remote speaker - both similar prices to UHF - and most now come factory tuned, so it's plug and play in most cases.

I'm not advocating we all abandon UHF - for short distance veh-to-veh comms and trackside comms with line of sight, it's probably superior - and certainly cheaper to add hand held units; but in my new rig I will definitely be adding a 27 MHZ Cobra unit - for that extra safety in remote areas, and ability to tap into the truckers network for long distance traffic updates. Also for those who go boating, most marine applications are 27 meg or VHF.

As a final note, the ebay dealer I quoted above and who specialises in 27MHZ SSB, advised that in the last 12 months he's seen a steadily building re-interest and growth in uptake of 27 meg.

Heck, with possibly national pickup, if enough of us get one we may end up with a mobile aulro.com club station - if there is interest :cool: !

Look forward to hearing your experiences and views on this. Cheers, Gav

[adonuff]

Hi I have both UHF & 27 meg SSB, The UHF is clearer but useless around Melbourne, too many idiots who spoil it for everyone else. The 27 meg is now very quiet, often when I swith it on all I get is silence.

It still works well I have spoken to most Australian states including Tas. Once out near Alice Springs there was no mobile phone reception, no UHF but I was still able to use the 27 meg on ssb.

I wouldnt suggest it as a reliable means of communication as long distance is influenced by weather conditions.

I like your idea it would work well.

Andrew

[d@rk51d3]

I thought that SSB still transmits in 5 watt, but because it only uses part of the wave as carrier, as opposed to the full wave for basic AM, it had the effect of a higher wattage.

I'll have to dig out the books and check again.

And, Yes. A SSB network would be interesting.:cool:


EDIT.

From the Adelaide Hills, we used to speak with guys in the US quite often with our base unit, as well as other far flung places.

[Gav110]

I thought that SSB still transmits in 5 watt, but because it only uses part of the wave as carrier, as opposed to the full wave for basic AM, it had the effect of a higher wattage.

I'll have to dig out the books and check again.

And, Yes. A SSB network would be interesting.:cool:

From the ebay seller's website - relating to the Cobra:

40 AM and 80 SSB Channels - 40 AM, 40 Upper Side Band, 40 Lower Side Band 4 Watts AM, 12 Watts SSB - The maximum allowed by law. SWR Calibration - Allows calibration of antenna system for maximum performance. 9 Foot Mic Cord - For easy reach within any area of the vehicle. Front Microphone Connector - Allows convenient installation to be in dash or under dash. Tone Control - 3 position control allows fine tuning of audio levels. Adjustable Dynamike Boost - Dynamically boosts microphone for increased voice clarity. Tactile Controls - Allows you to actually feel where the dial is in it's rotation without taking your eyes off the road. PA Capability - Use CB radio as a Public Address System with PA speaker. Receive signals can also be monitored through PA. RF Gain - Adjusts receive gain in weak and strong signal areas. Switchable Noise Blank - For increased noise reduction.

Great to hear we have at least 3 of us for an AULRO network !

All we need to do is pick a club landing channel and make it ours... ! :cool::cool::cool:

[Mick_Marsh]

Back in the old days....
Many times I and my friends have spoken on sideband to someone on the west coast of America from a car on a 5ft helical (when the conditions were right).
I still have my old Pearce Simpson Super Cheetah.

[DeanoH]

Belt Pulley drives on tractors were a great thing back in the'40's. They allowed farmers more flexability and cost saving in the powering of pumps, saws and sundry other equipment. Technology improved and now the belt pulley is a thing of the past, replaced by the PTO. It's the same with 27 Mhz CB.
Like many others I had my CB radio back then, a Johnston Viking, PLL front end for zero drift it was a great piece of kit. You could even work out the 'binary' coding of the tuner and create your own out of band private channels. But like the Dodo it couldn't evolve due to it's inherrent limitations and became extinct. VAS 980 or was it 981? that was me.
The reason 27 Mhz CB became extinct was basically because it was unreliable (you could talk to your neighbour one day but not the next but you could talk to someone 100 miles away), complicated (tuning in SSB signals could be a nightmare), inefficient (AM is a huge waste of spectrum) and complex ( most users had no idea of the relationship between AM, USB and LSB which led to confusion, frustration and unreliable communications.
To use a 27 Mhz CB effectively you needed to have some theoretical knowledge of radio transmitters. When you transmit on AM you actually transmit three signals. The carrier frequency, the carrier frequency plus speech (USB and the carrier frequency minus speech (LSB. This is very wasteful of power and bandwidth as all the information is in either sideband. So if you can suppress the carrier and delete one sidband you can put all of your legally allowed power into one sideband and have a much better signal. This is why the power allowed on SSB is higher than AM. The actual radiated power (AM and SSB is the same. Unfortunately all it needs is one person nearby to use AM at the same carrier frequency as you and your mate on the other sideband and you're both gone.
UHF FM was a far better idea. Better use of spectrum allowing more channels, smaller aerials, better quality speech more flexability, CTCSS Selcall etc. But best of all reliability. You now had reliable comms. The bloke you spoke to yesterday you could speak to today and tomorrow as well. UHF is line of sight, and isn't bounced of the ionosphere (skip), to screw up not only your comms but also someone elses several hundred miles away.
As for "and thousands of truckers still use it", you've got to be kidding, for the reasons outlined above.
".............I will definitely be adding a 27 MHZ Cobra unit - for that extra safety in remote areas". Only if you're totally suicidal. It doesn't have the reliability, the range or someone listening at the other end. Don't even think about it.
.............."and ability to tap into the truckers network for long distance traffic updates". Pure fantasy.

"- in clear atmospheric conditions, ranges of 50-100 KM are common, and where the cloud conditions are right and create enough skip, you're reaching people all round the country - in a mobile, whip antenna set-up"

Theres no doubt a bit of fun can be had, the challenge of taking advantage of ionospheric conditions to talk long distance. If on the off chance there is someone to speak to at the other end. But for this sort of game you're going to need somethig better than a whip antenna, the most inefficient of all antennas. Work out 1/4 wave at 27 Mhz, and you'll need two of end to end, makes it a bit hard to point in the right direction.

Don't mean to rain on your parade Gav but 27 Mhz CB is not serious communications. :)

Deano

[Mick_Marsh]

I take your point Deano.

Back in reminiscing mode: Back in those days, there was no internet, no fora to post on. ABC, Bill Collins' movies and a good long chat with the parents were the most obvious options for a Saturday night. Fiddling with a sideband CB was most interesting for a young lad which, for many of us here, probably led onto owning a Landrover.

Some of us do like to look back into and experience the past. Its a good way to see how far we've come.

[Blknight.aus]

ahhh yes, death of a good thing due to the lazieness of society to learn a skill set when something cheaper with half the abilities can do the job with less experience.

I know what kind of radio's Id rather have with me if I was stuck somewhere.

[Sprint]

I know what kind of radio's Id rather have with me if I was stuck somewhere.
yes, but if you were in the FFR they tend to be mounted in, whats the chances of getting stuck?

[d@rk51d3]

40 AM and 80 SSB Channels - 40 AM, 40 Upper Side Band, 40 Lower Side Band 4 Watts AM, 12 Watts SSB - The maximum allowed by law.


Just looked up my book............. and you're correct.:cool:

Am (full band) 4-5 watts.
SSB (upper or lower band) 12 watts.

Learn something new every day.;)

Finding a good mobile antenna is the big problem.
This is the rig I have: http://cgi.ebay.com.au/UNIDEN-GRANT-40-CH-AM-SSB-CB-RADIO-CAR-4WD-HOME-BASE_W0QQitemZ370306759705QQcmdZViewItemQQptZAU_El ectronics_Radio_Equipment?hash=item563800bc19

[dickyjoe]

I was somewhat late getting into the radio game, but as it has been mentioned above probably also relates to the owning of a Land Rover.

My unit which I still own the set, box it came, receipt, and a nice antenna was originally installed in the center of my EH panelvans roof. Its a Uniden PC 122XL and I love it too. Was quite common for me to be chatting to people in other states with it. I commonly chatted to school friends on it who were 50ks away.

I still think they have there place, and the fact that a lot of people don't use them makes it better when on a trip etc.

Rich

[Gav110]

Like I said, I accept that newer formats are technically better, and if I was crossing a desert solo I'd probably take a sat phone, but I think there is a place for these units as a secondary fit.

Anecdotal feedback suggests that there are several channels which are monitored by the devoted band of supporters, hence making this at least no worse than having no SSB unit, and in all likelihood better and more helpful for the odd time you are stuck miles from nowhere with no other comms.

Add to that more free channel space over a less densely used spectrum, and the ability to patch into coastal boating frequencies, and I think it's an interesting and rewarding secondary radio.

I also agree with the sentiment that they offer interest and a measure of exclusivity to a club like ours - Defender members especially generally tending towards being a) more technically minded b) less inclined to go with the flow and c) looking for ways to improve our vehicles and have a bit of fun.

I'm willing to give it a shot.

[Blknight.aus]

yes, but if you were in the FFR they tend to be mounted in, whats the chances of getting stuck?

given the amount of extra gear that I'd take, pretty good. :)

I was meaning limited to the uhf/am band radios in this case.

but a good HF set with a good antennae set is very hard to beat.

BTW...

want to know what happens when a rushlish and english speaking radio operator stumble onto each other frequencies on an exercise?

[MacMan]

Just looked up my book............. and you're correct.:cool:

Am (full band) 4-5 watts.
SSB (upper or lower band) 12 watts.

Learn something new every day.;)

Finding a good mobile antenna is the big problem.
This is the rig I have: UNIDEN GRANT 40 CH. AM SSB CB RADIO - CAR 4WD HOME BASE - eBay CB Radios, CB Radio, Radio Equipment, Electronics. (end time 15-Mar-10 05:50:14 AEDST) (http://cgi.ebay.com.au/UNIDEN-GRANT-40-CH-AM-SSB-CB-RADIO-CAR-4WD-HOME-BASE_W0QQitemZ370306759705QQcmdZViewItemQQptZAU_El ectronics_Radio_Equipment?hash=item563800bc19)

I still have one of these. Nearly sold it a couple of years ago just to have one less box of stuff. I might get it and the 1/4 wave out again!

[LowRanger]

Hmmmm must have been a different radio that I learnt about all those years ago.
At full modulation the carrier in an AM signal requires two thirds of the power but conveys no information. The second side band can be viewed as rebundant (overlooking frequency-selective fading in an ionospheric transmission path, that may distort one side band at times). Interference between several carrier frequencies, resulting in steady audio whistles or 'beats' is another disadvantage of AM.
Power may be saved and the band occupied by an AM signal in the frequency spectrum can be halved if only one side band is transmitted without carrier. The result is single side band suppressed carrier signal, called simply single side band signal (SSB ) transmission.
The carrier must be reintroduced at the receiver in such systems and closely adjusted to the original carrier frequency to avoid signal distortion. The introduced carrier carrier must be within 10 or 20 Hertz of the original carrier frequency for adequate intelligibility of voice signals, and stable oscillators are needed for generation of the local carrier.
For SSB the transmitter does not need to generate carrier power, and ratings are in terms of peak-envelope-power (PEP), the power capability at the peak of the modulating signal with linearity of the amplifier is maintained. For equal information content, and 100% modulation, the SSB signal requires only 1/6 th power of the double side band signal. However, the situation is even more favourable to SSB when speech is transmitted. Speech is not a continuous sine wave, and its average power is low with respect to its peak requirements. A peak-to-average power ratio of 10:1 is often assumed for speech, and under that condition, a Double Side Band (DSB ) AM signal would require 1.05 times carrier power, whereas for equal intelligibility the SSB signal would require only 0.05 units of power or 1/21 as much.
Because of the lower power rating, circuit components designed for SSB equipment can be smaller and lower in cost.
For generation of a modulated signal without carrier, a balanced modulator is used. A filter then discards one side band.


And as far as more channels go,I could swear that my 27Mhz radio has 40 channels which just happens to be the same amount as my 476/477 Mhz radio has.But then again I have UHF and VHF as well as HF radios that have variable VFOs and no channels as such,just an oprerating frequency.


And I am sure that it takes no more "Theoretical radio knowledge" to operate a 27 Mhz HF radio than what it does to operate many of the complex controls for setting sell calll and tone control etc on the average 476/477Mhz CB radio.


And yes I have been around radios for longer than I care to think about,back when valves were king,especially on the amateur bands,and way before the Johnson Viking was available with its pll circuitry,we were using cb's that were crystal locked,to set frequencies,but like most things,there were ways around this as well.
And the main reason that 27Mhz cb was all but abandoned by the government,in favour of the 476/477Mhz UHF was NOT for better use of the spectrum to allow more channels,BUT because of the interference generated across the spectrum in the second ,third and 4th harmonics,causing problem with industry and much of the electrical equipment that was coming onto the market,and also to sensitive electronics found in Hospitals etc.But this sort of interference still goes on!!!!! Ever wonder why you have to turn your phone off in a Hospital?


And by the way,if you really want efficiency,you should check the VSWR on your UHF antenna and feedlines,as there is nothing magically different,and no different rules apply just because of the different operating frequency.


Wayne
VK2---
exVK0---





[QUOTE=DeanoH;1180749]
To use a 27 Mhz CB effectively you needed to have some theoretical knowledge of radio transmitters. When you transmit on AM you actually transmit three signals. The carrier frequency, the carrier frequency plus speech (USB and the carrier frequency minus speech (LSB. This is very wasteful of power and bandwidth as all the information is in either sideband. So if you can suppress the carrier and delete one sidband you can put all of your legally allowed power into one sideband and have a much better signal. This is why the power allowed on SSB is higher than AM. The actual radiated power (AM and SSB is the same. Unfortunately all it needs is one person nearby to use AM at the same carrier frequency as you and your mate on the other sideband and you're both gone.
UHF FM was a far better idea. Better use of spectrum allowing more channels,

[Bushie]

Still got a 27meg set in the defender, but no aerial at the moment. Only 27meg AM though.


Martyn

[Blknight.aus]

And as far as more channels go,I could swear that my 27Mhz radio has 40 channels which just happens to be the same amount as my 476/477 Mhz radio has.But then again I have UHF and VHF as well as HF radios that have variable VFOs and no channels as such,just an oprerating frequency.


for a standard off the shelf unit, yes but within the upper and lower limits of the band you can operate where you want if your unit has the ability. for the other bands that you're required to be licensed to use you need to stay in the "steps"



And I am sure that it takes no more "Theoretical radio knowledge" to operate a 27 Mhz HF radio than what it does to operate many of the complex controls for setting sell calll and tone control etc on the average 476/477Mhz CB radio.


For LOS or NOTH whip to whip yes, setting up to do darwin to adelaide though.......

[GRIFF]

I thick the kiwis still play with am radios as they work ok in the mountains

[cewilson]

Still got a 27meg set in the defender, but no aerial at the moment. Only 27meg AM though.


Martyn


You and me both :cool:


And funnily enough there's still quite a few people that I do trips with that still have one in their vehicle :angel:

[DeeJay]

Yes we all used them in 1976..Those that could afford them. Both truckers & 4wders. SSB was no good up close ( up to 500m it would distort) & AM was useless above about 5klm. So in loose convoy you were forever swapping bands, not knowing what the others were using. I remember buying mine from a shop in Russell St Melb & taking it back to get it tuned & the seller put out a call for others "20" & got Hawthorn ( 3klm) & Middle Park ( 5klm) That was on the call channel. 2 years later no one would talk to you & there was that much clutter you could only wish to get such range anyway.
I kept mine for quite a few years after that as I could get skip & felt if I got stranded at least I might be able to get a message out. But it was iffy because the person you were talking to ( usually 500k,1000l,1500k etc) would suddenly disapear, it could be 5 or 15min.
They were great as you could soon pick up the vibe in any town & get invited to a BBQ or Pi$$up pretty quickly, those days are long gone:(
Nowadays with UHF & mobile phones, I reckon they wouldn't be worth installing. I thought they were not able to be sold ie sublimely phased out ??.

[scott oz]

Run both.

Good fun :D inexpensive and not big uits.

[Sleepy]

Yep as mentioned elsewhere SSB 27Mhz is becoming more inviting now all the yahoos have moved up to UHF. SSB is a different MODE to AM. And UHF CB (477Mhz) is in FM, a different mode again.

They all have there advantages, with UHF CB being the best, IMHO, for convoy ops. (Less interference, shorter wavelength and therefore antenna and no need for fiddly fine tuning.)

SSB HF (27 MHz) operates on the 11 metre wavelength therefore effective antennas are generally longer (get caught in trees, break fluro tubes in the garage, can be a bit fiddly to fine tune)

AM 27Mhz transmits a carrier + two side bands. THe information (voice) is transmitted by modulating the amplitude of the signal (Hence "A-M") This is why it is a third of the wattage. Key the mike on AM and it will transmit a carrier (Everyone who has used AM CB will have had someone "Drop a carrier" on them and the resulting hetrodyne makes a hellavu noise)

SSB will only transmit the full 12 watts when you are at full modulation. Ie Try and "drop a carrier" on SSB and nothing will happen. "Power Mikes" were the bee knees in the 70s - they boosted your modulation and effective output.

In the right conditions radio wave will bounce (or skip) off the ionosphere - much more likely on HF. (30Mhz or lower)

If you have got this far, think about this.

An amateur (or ham) radio license is now much much easier to obtain. You can have all the fun of HF, VHF, and UHF by doing a simple course (usually a couple of weekends at your local amateur club) and you will qualify for a foundation license.

(When I did it you needed to do Morse code and fairly lengthy electronics exam)

Ham Radio is bags of fun if you like playing with SSB CB, here is a link for more info The Wireless Institute of Australia (http://www.wia.org.au/)

73's
VK3GPS

[Frenchie]

Well I hope they are coming back, I have a lovely Uniden PC 122XL which I would love to sell. :cool:

[dullbird]

be nice if they did...I have a midland that I bought over from the uk very little tidy unit which was also chipped for europe which gave a hundred more channels

[Tombie]

Geez.. Flash backs...

Stupid call signs, mobile setups..

1000w Linear amps, skip whips, 9' stainless whips... Megatrons, homebases...
Car mounted (yes) 3 element Yagi's...

Parking at Lofty with homebase antenna mounted on cars...

Digiscans, Extra channels, slides.....



Oh the horror!!!!!!!! :angel:

[VladTepes]

ahhh yes, death of a good thing due to the lazieness of society to learn a skill set when something cheaper with half the abilities can do the job with less experience.

I know what kind of radio's Id rather have with me if I was stuck somewhere.

Like how to properly drive. Easier just to buy a D3..... :wasntme:

[Tote]

It's interesting that HF radio is gradually dying as well. Lots of Govt sites are being decommissioned and replaced with satellite comms. Makes me wonder what sort of dire straits we would be in if the sattelites suffered a major outage.
It would be interesting to see what could be done if the same amount of research was put into HF as has ben expended on ADSL over the last 10 years. A communications format that had a bandwidth of about 4k is now transmitting 8kb/s and more.
Regards,
Tote

[Blknight.aus]

Like how to properly drive. Easier just to buy a D3..... :wasntme:

Or a puma.....:angel:

[Armadillo]

Parking at Lofty with homebase antenna mounted on cars...



Ummm...not Mount Lofty???....:eek::eek::eek:

[loanrangie]

Back in the old days....
Many times I and my friends have spoken on sideband to someone on the west coast of America from a car on a 5ft helical (when the conditions were right).
I still have my old Pearce Simpson Super Cheetah.

Me too, a uniden super panther i think it was mounted on my motorbike i would sit up on Mt Dandenong and talk to guys in the airforce base in Hawai on a good night . Still have the CB in the cupboard and a base station antenna- will have to drag it out, i know it still works.

[Tombie]

Ummm...not Mount Lofty???....:eek::eek::eek:

Yep :cool:

[Mick_Marsh]

Me too, a uniden super panther i think it was mounted on my motorbike i would sit up on Mt Dandenong and talk to guys in the airforce base in Hawai on a good night . Still have the CB in the cupboard and a base station antenna- will have to drag it out, i know it still works.
You would have seen the Super Cheetah still mounted in the SIII Stage I on the weekend.

[Redback]

Back in the old days....
Many times I and my friends have spoken on sideband to someone on the west coast of America from a car on a 5ft helical (when the conditions were right).
I still have my old Pearce Simpson Super Cheetah.

I still have 2, 27meg radios, a 40 channel GME in the Disco and a Ferris 5000 with a 200 channel digiscan at home;)

Baz.

[Sleepy]

You guys would be amazed at what those old CBs are worth nowadays. I saw a super cheetah sell on ebay for over $200 - very collectible. Especially if they have lots of chrome. Used to buy them in cash-converters for $20 :angel:

[loanrangie]

I think i will get the uniden out and stick it in the disco, got it for my 21st back in 1989 :o.

[d2dave]

I think i will get the uniden out and stick it in the disco, got it for my 21st back in 1989 :o.

My first cb was also a 21st present. A realistic(Tandys Brand)23 channel.

40 channels were not available back then. They were also illegal at the time which made them much more fun.

This thing actually got me sacked from my job as I would be on it half the night and always late for work.

I later upgraded to 40 channel sideband which was in my rangie. I sold the vehicle about five years ago and I could not be bothered pulling it out as it was basically obsolete.

Dave.

[p38arover]

My first cb was also a 21st present. A realistic(Tandys Brand)23 channel.

40 channels were not available back then.

Mine was a Sanyo 18 channel unit.

[Redback]

Mine was a Sanyo 18 channel unit.

My radio way back then was a HMV Roadhound 18 channel.

Baz.