Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

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g8tzl2004
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Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by g8tzl2004 »

A VHF CDM covers from 136 to 174 MHz (ie a 38 MHz range)

A UHF CDM covers from 403 to 470 MHz (ie a 67 MHz range)

A "10m" Low Band CDM covers from 29.7 to 36 MHz ( ie a 6.3 MHz range)

So why is the low band CDM coverage so small? Why do you need 3 different radios to cover from 29.7 to 50 MHZ (ie a 20 MHz range in total) rather than just one radio?
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Astro Spectra
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Astro Spectra »

Let's look at the tuning ranges 38/136 = 28%, 67/402 = 16%, 6.3/29.6 = 21% so the low band coverage doesn't look out of line to me.

To cover wide percentage frequency ranges takes a lot of design effort. If you want a commercial Motorola radio that does 10M and 6M get a Syntor.
g8tzl2004
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by g8tzl2004 »

Thanks for the explanation looking at percentage coverage.

But why can a Syntor X9000 do the full low band in one radio :)...as well as certain Kenwood radios!!

It also seems a lot of manufacturing effort to have 3 different radios for one band when one radio could do it all...as with various mil radios!!?
Last edited by g8tzl2004 on Fri Aug 25, 2017 2:45 pm, edited 1 time in total.
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Astro Spectra
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Astro Spectra »

It's volume driven; in very high volume manufacturing it doesn't matter having multiple variants.

Mil radios are completely different, a 30 to 88 MHZ CNR even without ECCM costs 10x to 40x times a commercial radio price.
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Bill_G
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Bill_G »

Percentage of Freq of interest already explained.
Adding to the economics - most customers do not move around the sub-bands much. They get their license, and they use the radio like an appliance. So, they appreciate a lower cost radio. Why sell something they will never use?
g8tzl2004
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by g8tzl2004 »

I always thought a mil radio costs 40x a commercial radio because the government is paying for it !!! :)

Mind you APX8000's are not cheap :)
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Bill_G
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Bill_G »

OTOH, the civilian applications that sprang from military specifications are all through modern two way radios. Those wideband UHF and VHF VCO's you love came from research dev'd for MILCOM first. There was a time when VHF radios came in several sub-bands, and UHF came in at least two splits.
com501
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by com501 »

Nah, it's all about salesmen's commissions! :)
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train_radio_guy
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by train_radio_guy »

If you really want a broadband radio, and money is no object, try either a Wulfsberg http://www.wulfsberg.com or Harris Military Tactical Multiband Radios http://www.harris.com/solution-grouping ... and-radios. Either of those will save on the headache of needing RSS/CPS, cables, RIBs, and a computer that is of the correct vintage to correctly run the RSS/CPS.

You'll still have to address the antenna system, for resonance relative to the band of frequencies, on which the radio is operating. That being said, I'm sure both Wulfsberg & Harris have their own respective antenna solutions as well.
"Trust me, I know what I'm doing!" - Sledge Hammer
com501
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by com501 »

The antenna for my RT-5000 was $6400. I didn't even get a t-shirt.
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Bill_G
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Bill_G »

Yeah, but the antenna is very slimming.
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train_radio_guy
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by train_radio_guy »

g8tzl2004, if you really want a radio that covers 30-50 MHz, for 'receive' only purposes, there are a few high-end Amateur Transceivers, which fit the bill (no pun intended) quite well. They are the Yaesu FT-650 (24.5 - 56 MHz) & the ICOM IC-575H (26-56 MHz). They’re both all mode units (i.e. FM, AM, SSB, & CW), & while they could be used mobile, they're better suited for base operations. Unfortunately, both units have been manufactured discontinued for quite some time, but occasionally surface at hamfests & on eBay.
"Trust me, I know what I'm doing!" - Sledge Hammer
g8tzl2004
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by g8tzl2004 »

OK train_radio_guy on the ham radio receivers for 30 - 50 MHz. I think my FT817 and IC706 can RX between 30 and 50 MHz? I'm not sure about my TenTec Eagle? I was mainly wondering why Motorola took the trouble to build 3 slightly different radios for 30-50 MHz rather than having just one radio that does it all - but the other posters have provided answers.
g8tzl2004
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by g8tzl2004 »

OK train_radio_guy on the ham radio receivers for 30 - 50 MHz. I think my FT817 and IC706 can RX between 30 and 50 MHz? I'm not sure about my TenTec Eagle? I was mainly wondering why Motorola took the trouble to build 3 slightly different radios for 30-50 MHz rather than having just one radio that does it all - but the other posters have provided answers.
motorola_otaku
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by motorola_otaku »

I found the RX sensitivity on the 706 in the 30-50 range to be lacking, but that may have just been my experience with one radio.

OP: there's a reason why Kenwood is still in the low band business and Motorola isn't. It's a niche market and they don't care. Give the Kenwood TK-690 a whirl... it's a solid radio, and every bit on par with a Maratrac or CDM. GE/Harris Orions are another option, if you have access to Programmer and don't mind doing a little modding to move one up to 6 meters. I'll personally vouch for both.
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Astro Spectra
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Astro Spectra »

+1 on the TK-690H, I have one on 6m sharing a control head with a 890. Solid 100W mobile. I can also recommend the TK-6110. At 70W it's lower power but you can cover 10m and 6m (with modifications) in one radio and it's a heck of a lot smaller than a low band Syntor.
g8tzl2004
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by g8tzl2004 »

I checked the specs of the TK-690H and it officially covers down to 29.5 MHz with no mods...so I guess its OK for most of the 10m FM band without any hex editing...although maybe its easy to program a Kenwood out of band anyway?
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train_radio_guy
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by train_radio_guy »

Finding Low Band VHF Radios, that truly cover 30-50 MHz with no gaps & good sensitivity can be a challenge, but they are out there, whether you're talking Commercial/LMR, Amateur, or Military. I also had a GE-Ericsson Orion on Low Band, and it performed very well, both in sensitivity & power output. Regrettably, I sold it & have kicked myself for it ever since! I especially liked their control head's VFD - crisp & easy to read.

While I have not had much experience with Kenwood Radios on Low Band VHF, the few UHF mobiles I've owned over the years were solid performers, & easy to use.

Some folks may have written-off the commercial side of Low Band, but there are a number of customers/users, which still use it in their day-to-day operations. I guess it truly depends on the end-user's application. As they say, if the shoe fits..... ;)

- trg, 8)
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Jim202
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Jim202 »

You want a low band radio for the entire low band, try stopping by your local Motorola service shop. The older they are they more your chances are of finding one of the old radios. What your looking for is a low band Syntor X9000. You may be able to find some Syntor X radios. But don't be surprised if they tell you they threw all those in the dumpster many years ago. You can find them on several of the for sale web sites. But don't pay much for them.

The Syntor X radios will require you to purchase a replacement board for the frequency PROM. I think these boards are made by Pie. But could be wrong. They take the place of the original memory plug in board and allow for computer programming the scan and frequency information.

These radios basically use the same RF portions, it's just the control board that is different. But they will play well once you get them up and running.

Both versions of these radios will cover the entire low band segment from about 29 MHz. all the way up to just about 54 MHz. No tuning and 100 watts out of the transmitter. You big problem will be how to handle the antenna that will give you a low SWR.

If your looking for a radio that will do both 10 meters and 6 meters in the same radio, these will do it. I have several in use both at home and in my truck. There are some dual band antenna boxes that you have one port in and two ports out. One for the 10 meter portion and one for the 6 meter portion of the band. Then install 2 antennas.

There is software available and you can make the programming cable yourself. You will need a RIB to go between the DOS computer and the radio programming cable. The RIB uses a serial cable, but all the older computers that can run DOS will have the serial port.

Just remember that you will need a hard drive in the computer that is no larger than 80 GB. Plus it needs to be formatted in the FAT32 format. I generally make 2 partitions on the hard drive. On that is about 20 GB in size for the DOS portion and use the rest to run Windows XP in. That way I can use the abilities of the XP to be able to transfer files between my many computers via an Ethernet connection.

Have fun and enjoy the Syntor radios.

Jim
mike m
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by mike m »

com501 wrote:The antenna for my RT-5000 was $6400. I didn't even get a t-shirt.
At least you have an antenna and working radio.

I designed the original RT5000 transmitter module and other comm radios in Prescott over the years 1990 to 2011 and in the entire time I worked for Wulfsberg through ownership by Sundstrand Data Control, Allied Signal (allibie signal), Chelton and finally Cornhole-Cobham, I never had a 100% working radio nor any working antenna to play with.

In fact the only time I ever saw and got to play with a working RT5000 was when visiting the Oregon National Guard next to my present work facility during an open house event for the New Lakota UH-72 LUH helicopter introduction 5 years ago.

And I didn't get a tee-shirt either, got nothing at all from Corn-Cobham when I left.
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syntor9k
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by syntor9k »

I have a FT-857d and it covers approx 1.6-33 MHz, and 33-56MHz, RX/TX after changes are made.
http://ku4by.com/yaesu-857d-mars-mod/
George
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by George »

[quote="g8tzl2004"]A VHF CDM covers from 136 to 174 MHz (ie a 38 MHz range)

A UHF CDM covers from 403 to 470 MHz (ie a 67 MHz range)

A "10m" Low Band CDM covers from 29.7 to 36 MHz ( ie a 6.3 MHz range)

So why is the low band CDM coverage so small? Why do you need 3 different radios to cover from 29.7 to 50 MHZ (ie a 20 MHz range in total) rather than just one radio?[/quote]

The real reason for this is due to Motorola not having built a VCO that can do what an X/X9000 VCO can do and lock with the speed needed to do really good scanning.

Power amp and front end bandwidth is one thing. VCO stability over the range is another.

Bottom line: Everything BUT the X/X9000 was tested, was measured and was found to be wanting. Hence three (or more) bands.
Karl NVW
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by Karl NVW »

The receive side is easy - you just need an SDR-RSP2 and SDR UNO software and a laptop to run it. Price is about $150 USD. But that ignores the antenna system which needs to provide a nominal 50 ohm impedance to the radio for transmit (RL<15 dB), across the entire 30 to 50 MHz window, and develop less than 10 dB loss, not just act like a dummy load. Also realize that you are arguing the merits of a product design that is three decades old which you can only acquire as scrap salvage.
Karl - WA8NVW AFA5VB
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brickster
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Re: Low band CDM - why do you need 3 radios to cover from 30 - 50MHz?

Post by brickster »

For the OP, this question of yours about band coverage was quite a topic in my day, and not just for those converting commercial radios for the amateur frequencies. I used to analyze production defects in Motracs in Schaumburg. I know they stretched those bands to get just as much coverage as they could using slug-tuned filters, because each of the 4 ranges in low band got near the center of the range in pre-test, but often fell out in final test with the customer's channel elements. Slugs approaching but not peaking in the center of the coils, or falling out the end. State of the art of variable inductors.

Later, in the field, I did a few band changes for customers who acquired radios. Tracs and at least one Micor. No T-powers! It was expensive for the end user, but not nearly so much as a new radio. We had to install two radios if they wanted to talk on two bands. Anyway it is good question put by many in my experience.
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