VHF vs CB Antenna?
MikeT1946
Band (CB). The former owner kept the CB. So I now have 3 antennas, and 2
things to hook them up to.
The question is, can I hook the VHF up to what had been used as the CB
antenna? They're both white plastic whip antennas, and I have no idea
whether they're electronically different in any way or not.
Radio experts? Thanks...
-- Mike
Rhett Westerman
different.
P.Bennett
>
>The question is, can I hook the VHF up to what had been used as the CB
>antenna? They're both white plastic whip antennas, and I have no idea
>whether they're electronically different in any way or not.
>
No, you should not use the CB antenna with a VHF radio, or vice versa.
An antenna is designed to operate at a particular frequency, and will not
operate correctly at a widely different one. CB radio operates around 27 MHz,
and Marine VHF is around 157 MHz.
Peter Bennett VE7CEI | Vessels shall be deemed to be in sight
Internet: ben...@triumf.ca | of one another only when one can be
Packet: ve7cei@ve7kit.#vanc.bc.ca | observed visually from the other
TRIUMF, Vancouver, B.C., Canada | ColRegs 3(k)
Steve Weingart
mike...@aol.com (MikeT1946) wrote:
>I just bought a boat that had been equipped with Loran, VHF, and Citizen's
>Band (CB). The former owner kept the CB. So I now have 3 antennas, and 2
>things to hook them up to.
>
>antenna? They're both white plastic whip antennas, and I have no idea
>whether they're electronically different in any way or not.
>
>
>
CB is 27 mHz, VHF is in 150's to the 160's, so you cannot use the same antenna
directly since the electrical tuning doesn't match. There are antenna
matchers/coupler/tuners that you can buy to match the antenna to the radio,
but these usually give less than great results unless you get a really good
ham type antenna tuner which costs more than either the CB or the VHF.
If you do decide to go with an antenna tuner, make sure that you borrow/get an
SWR (standing wave ratio) meter to test the tuning. If the antenna does not
match the transmitter, the power reflected back into the radio can cause
overheating or damage to the transmitter. The meter ($25) will make sure that
it's right. Actually it's a good idea to get an SWR meter and to test you
antenna a few times a year. It will alert you to a bad antenna connection
without haveing to go to the masthead ;-)
I would leave the CB and the VHF on a separate antennae for the best
performance with the least overall hassle.
Steve
Malcolm Osborne
>I just bought a boat that had been equipped with Loran, VHF, and Citizen's
>Band (CB). The former owner kept the CB. So I now have 3 antennas, and 2
>things to hook them up to.
>
>The question is, can I hook the VHF up to what had been used as the CB
>antenna? They're both white plastic whip antennas, and I have no idea
>whether they're electronically different in any way or not.
>
>Radio experts? Thanks...
>
>
CB uses a frequency of 27MHz, which has a wavelength of about 11m. A
half-wave whip antenna would have to be 5.5 m, but of course shorter ones
could be used if they were matched correctly (built-in loading
coils,etc.) VHF uses frequencies in the order of 140 - 15 MHz, with
wavelength about 2m, 1/2 wave being 1m. Again, the length can be reduced
by means of loading coils). Thus it is possible to have VHF and CB
aerials the same length, but one would not work with the other as the
antenna characteristics are incorrect (i.e. are frequency dependent).
I'm not familiar with the frequncies used by LORAN.
--
Malcolm Osborne
Pretoria South Africa
EMail: osbo...@telkom03.telkom.co.za
Ronnie L. Hoover
ohms. I am not exactly sure what the VHF is but it IS not 50
ohms.
Michael Frere
I think your talking about the caracteristic impeadance of the
cable and the antenna. Both CB & marine VHF are 50 ohms.
Also both bands are closely located in the MID-VHF band.
Technicaly, using a CB antenna should work. However, there are
other considerations that should be taken, like the environment
that they are used in (salt water), how much gain the antennas
have, how they are mounted, etc.
To be sure that no damage is done to either radio, I would
check the VSWR meter on the radio (if it has one).
Or I would measure the forward and reverse power (with a power
meter that operates in that band and the Power Amp is keyed)
and make sure a 10:1 ratio is not exceeded.
Hope this helps...Mike
P.Bennett
>Ronnie,
>
>I think your talking about the caracteristic impeadance of the
>cable and the antenna. Both CB & marine VHF are 50 ohms.
correct
>
>Also both bands are closely located in the MID-VHF band.
WRONG!! CB is about 27 MHz, and Marine VHF is 157 MHz.
>
>Technicaly, using a CB antenna should work. However, there are
No, a CB antenna _will_ _not_ work effectively for marine VHF, (even if it is a
"marine" CB antenna) and may damage the VHF transmitter.
Peter Bennett VE7CEI | Vessels shall be deemed to be in sight
Internet: ben...@triumf.ca | of one another only when one can be
Packet: ve7cei@ve7kit.#vanc.bc.ca | observed visually from the other
TRIUMF, Vancouver, B.C., Canada | ColRegs 3(k)
GPS and NMEA info and progs: ftp://sundae.triumf.ca/pub/peter/index.html
Larry DeMers
>Ronnie,
>
>I think your talking about the caracteristic impeadance of the
>cable and the antenna. Both CB & marine VHF are 50 ohms.
>
BALONEY! CB is 27 MHz, while Marine VHF is 150-160 MHz.
>
>Technicaly, using a CB antenna should work. However, there are
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Yup, until the final amp burns up due to the tremendous mismatch
caused by the reflected power!
>
>Hope this helps...Mike
>
Keep hoping Mike.. that he doesn't follow your advise and burn up his rig!
===============================================================================
Larry DeMers
S/V DeLaMer
Cape Dory 30 "Sailing the beautiful Apostle Islands of Lake Superior"
"It is dangerous to awaken a lion; The teeth of the tiger can prove fatal;
but the most fearsome of all is the human fanatic"...J.C.F. von Shiller
Steve Weingart
ben...@erich.triumf.ca (P.Bennett) wrote:
>In article <44clth$8...@limestone.kosone.com>, Michael Frere
<mfr...@limestone.kosone.com> writes...
>>
>>I think your talking about the caracteristic impeadance of the
>>cable and the antenna. Both CB & marine VHF are 50 ohms.
>
>>
>>Also both bands are closely located in the MID-VHF band.
>
>>
>>Technicaly, using a CB antenna should work. However, there are
>
a
>"marine" CB antenna) and may damage the VHF transmitter.
>
With the proper antenna tuner a CB antenna can be made to work reasonably
well, without any risk to the transmitter (except in the case of base loaded
CB antennas, the coil is tuned for the particular frequency and even if you
match it so you won't hurt the radio, the performance will be terrible). This
is done all the time by hams who use some arbitrary length wire (the backstay
usually) as their antenna. The main thing is that a good antenna tuner costs
more than either radio ;-) The cheap tin boxes that you can find at some
marine/car stereo/appliance stores, usually are not very good, and if they
don't hurt the radio, they will kill the transmission efficiency.
Steve
Richard Jarvis
CB Frequencies are HF (2-30MHz, with CB= ~26MHz).
You COULD use an impedence matching box to run a CB
on a VHF antenna, but there will be considerable loss,
as even with impedence matching the VHF antenna was
not designed for HF frequencies.
--
Rick Jarvis Tektronix, Inc.
Michael Frere
Sorry Ronnie but I've made a big mistake with the frequencies. CB radio is around the
27 Mhz frequency, not 160Mhz where the marine band is located. For some embarasing
reason I was thinking Trunked Radio!
Having said this I must retract my previous statement. You CANNOT use a CB antenna
for Marine VHF use (or vise\versa)! Of course you could use some Trunked Radio
antennas ;->
Sorry if I caused you and anybody else any problems...Mike
DOYLE SOUDERS
> Path: nsc!voder!psinntp!psinntp!psinntp!uunet!in1.
> uu.net!news.sprintlink.net!news.gate.net!sysop From: s...@gate.net
> (Steve Weingart)
> Newsgroups: rec.boats
> Subject: Re: VHF vs CB Antenna?
> Date: Thu, 28 Sep 95 12:07:25 GMT
> Organization: Electrical/Electronic Design Consulting Lines: 33
> Message-ID: <44e38o$1d...@news.gate.net>
> References: <25SEP199...@erich.triumf.ca> <DFJ0wD.9z0@
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> X-Newsreader: News Xpress Version 1.0 Beta #4
above is correct and Steve is on thin ice and I'm sure someone will point out
inconsistencies with my $0.02 but here it is. The frequency ranges for the
antennas are completely different. The characteristic impedance of 50 ohms is
only true for the a specific frequency and capacitance and inductance
combination. If the impedance is not 50 ohms for the antenna you are using at
the frequency you are using it, you will have a mismatch and the transmitter
energy will be reflected back into the transmitter output transistor and could
cause damage. It can cause excessive current or even voltages higher than the
supply voltage (remember this is RF) which can in turn blow the output
transistor. Now, what about an antenna tuner? The antenna tuner is an
impedance matching device and it will make it look like the CB antenna is
properly matched to the VHF transmitter (assuming it has the proper range of
adjustable capacitance and inductance) Since the impedances are matched you
will have no energy reflected back into the transmitter. Good?? Well, not
quite. The original goal was to get the energy from the transmitter into the
antenna and from the antenna into the atmosphere. All we have done with the
antenna tuner was get the energy from the transmitter into the antenna tuner!
With original mismatch on a tuned antenna very little energy actually gets
into the antenna and even less gets into the air. Bottom line is that good
antennas are worth what they cost. Some marine antennas have 6 db of gain.
That is a significant multiplication of your signal. It is accomplished by
tuning and design of an antenna to change its radiation pattern specifically
for a marine application. ( lower flatter radiation pattern)
The bottom line .... Don't connect a $150-$300 radio to an antenna that is not
designed for that application. You would have a better chance of success
with a $3 set of rabbit ears from a tv set.
Hopefully this has been constructive, no flames intended!
....Doyle KG6MY
Larry DeMers
When is the last time you have seen an antenna tuner on the market for
Marine band VHF? The antenna tuners that ARE out there are for HF, with
a top end of about 28-29 MHz. Falls a bit short of the 156 MHz. needed.
Darrell Irvin sptekwv2
|>
|> Haven't seen or looked for one recently, but I have seen them in the past(at
|> least I think I did). It used to be common for lake boats to use CB and VHF,
|> that was where I though that I saw them. BTW, like I said in an earlier post,
|> I wouldn't recommend an antenna tuner, the efficiency would be terrible. I
|> was just saying that it was an option.
|>
A fair number of boats here on the Columbia River also carry CB. I don't think I
have ever seen an installation which didn't use separate antennas on each radio.
--
= Darrell Boots Irvin bo...@orca.WV.TEK.COM =
= VND Engineering, Tektronix Inc. =
Rod Mc Innis
: Ronnie,
: I think your talking about the caracteristic impeadance of the
: cable and the antenna. Both CB & marine VHF are 50 ohms.
The impedance of the feed and antenna can be anything that the
engineer wanted it to be. There are three common impedances in use:
300 ohm, 75 ohm, and 50 ohm.
Television sets (at least the older ones) that had twin lead inputs
used 300 ohm impedance. Sets that use a coaxial input will use 75
ohm.
Most communication equipment that the average person will come in
contact with will be designed for 50 ohms, although there may be some
75 ohm stuff encountered ocassionally.
Coax cable is essentially frequency independent. The impedance will
stay roughly the same from some low frequency (but not DC) to very
high frequencies.
Antennas, on the other hand, are a tuned circuit and will only
exhibit the desired impedance at a specific frequency. Various
designs can make the antenna very efficient at a single frequency, and
very inefficient for just a small frequency change. Other antenna
designs will sacrifice peak performance for reasonable performance
over a "band" of operation. It is this later style of antenna that
they typical consumer would use.
: Also both bands are closely located in the MID-VHF band.
Not so. The CB band is down around 27 Mhz. Channel 16 on the
marine band is at 156.8 Mhz. We are talking a 6:1 difference here.
That is not what I would consider "close".
: Technicaly, using a CB antenna should work. However, there are
: other considerations that should be taken, like the environment
: that they are used in (salt water), how much gain the antennas
: have, how they are mounted, etc.
No way! The match between the CB antenna and the marine radio would
be horrid! He might as well take the antenna off and stuff a coat
hanger into the end of the coax.
: To be sure that no damage is done to either radio, I would
: check the VSWR meter on the radio (if it has one).
I have never seen a radio with a built in VSWR meter. Getting a
VSWR meter that will work on the marine band is not easy, and getting
one that works well would be very expensive. For the lower
frequencies (like CB) the VSWR meters are rather cheap, but the very
high frequencies require a better grade of components.
: Or I would measure the forward and reverse power (with a power
: meter that operates in that band and the Power Amp is keyed)
: and make sure a 10:1 ratio is not exceeded.
: Hope this helps...Mike
The bottom line is don't use an antenna for a radio it wasn't
intended for.
Rod McInnis
Steve Weingart
dem...@labman.cray.com (Larry DeMers) wrote:
>When is the last time you have seen an antenna tuner on the market for
>Marine band VHF? The antenna tuners that ARE out there are for HF, with
>a top end of about 28-29 MHz. Falls a bit short of the 156 MHz. needed.
Haven't seen or looked for one recently, but I have seen them in the past(at
least I think I did). It used to be common for lake boats to use CB and VHF,
that was where I though that I saw them. BTW, like I said in an earlier post,
I wouldn't recommend an antenna tuner, the efficiency would be terrible. I
was just saying that it was an option.
Happy Friday,
Steve
Darrell Irvin sptekwv2
|> Ronnie,
|>
|> I think your talking about the caracteristic impeadance of the
|> cable and the antenna. Both CB & marine VHF are 50 ohms.
|>
NOPE... Not correct. CB is about 27 Mhz while Marine VHF is around
150 Mhz.
|>
|> Technicaly, using a CB antenna should work. However, there are
A CB antenna simply will not work. It won't be anywhere close
to 50 ohms that far off its design frequency.
|> other considerations that should be taken, like the environment
|> that they are used in (salt water), how much gain the antennas
|> have, how they are mounted, etc.
The inexpensive Marine VHF antennas don't cost much more than a CB whip.
(antenna about $30). Beyond this you will need a mount ($15 in Plastic to
$40 in Stanless Steel).
|>
|> To be sure that no damage is done to either radio, I would
|> check the VSWR meter on the radio (if it has one).
Damage is possible, although some radios contain an built in SWR
circuit which is used to reduce transmit power in the case of
high reflected power. I had an antenna fail (old age) on my ICOM
radio. It acted very strange. Some simple investigation on a
known good dummy load pinpointed the problem.
|>
|> Or I would measure the forward and reverse power (with a power
|> meter that operates in that band and the Power Amp is keyed)
|> and make sure a 10:1 ratio is not exceeded.
|>
|> Hope this helps...Mike
|>
--
pvin...@health.co.lenoir.nc.us
Mr. Luddite
gfre...@aol.com
wrote:
Tim
gfre...@aol.com
wrote:
Over on the home repair group the homeowner web seems to be famous for
it.
dmjack...@gmail.com
Derek
Mr. Luddite
> I have a uniden CB radio (new) and have an existing larsen wb vhf radio already on my truck. Will this antenna work with my new radio.
> Derek
>
"cut" for. There are two VHF bands, low-band VHF (49-108 MHz),
high-band VHF (169-216 MHz). Marine radios operate in the high band.
Generally it will receive ok but transmit range may be limited due to
high standing wave ratio (SWR).
Even a marine VHF antenna should be tweaked in terms of length to
minimize SWR in the middle of the radio's freq range.
Tim
gfre...@aol.com
wrote:
>I have a uniden CB radio (new) and have an existing larsen wb vhf radio already on my truck. Will this antenna work with my new radio.
>Derek
The receiver might work but you are really stressing the transmitter.
Children's band antennas should be cheap, especially if you can find a
used one. My guess, most got thrown out with the leisure suits and
bell bottoms.
Try Ebay
gfre...@aol.com
the lowest frequency VHF.
SWR is really going to be ugly but since they are capped at 5w,
(usually more like 4.5) I doubt the magic smoke comes out but he won't
be "getting out" far either.
If his "truck" is a real one (breaker good buddy size) and he has 8-9'
from mirror to mirror the best antenna is the co phasers you see on
big rigs. Otherwise it is hard to beat a bottom coil loaded ~48"
antenna right in the center of the roof. That is what I had on my van
but you had to remember to take off the vertical when you went into a
parking garage. ;-)
Mr. Luddite
Thought he was talking about a new VHF Marine radio. But the antenna
issues remain the same. For max range whatever antenna he uses needs to
be of the proper length. At 27 MHz a full wavelength is about 103
inches. A half wave antenna would be about 51.5 inches long and
aquarter wave length antenna would therefore be about 25.75
inches.
If really anal about these things, an SWR meter should then used to trim
the antenna length to the lowest SWR on channel 20 (mid-range).
I have an old SWR meter from the CB craze years that I never use anymore
but for some reason it's one of those things I just can't throw away.
Bill
looking at a new radio for the boat. One with AIS. Maybe Santa Clause.
gfre...@aol.com
old 3d shift partner was a Ham/Navy ET so I got pretty good guidance.
;-)
He was an RF wizard.
He was the guy who left FE, went to IBM FSD, Lockheed, Loral and
worked in Germany for a decade or two and now retired in Colorado.
http://gfretwell.com/ftp/colorado/Greg%20and%20John.jpg
Three old guys on the top of the hill behind John's house, next to the
fence to Rocky Mountain Federal Park.
Another Navy guy doing well! I hope "Dutch" (the dog) is still OK
;-)
gfre...@aol.com
Worst case I call a tow pirate but I have plenty of neighbors who owe
me a tow.
Sinking is not an issue, we will just wade ashore, I will plot a
course through the mangroves with my aerial photos and boy scout
compass and we will walk home.
I do have loppers on the boat ;-)
Mr. Luddite
could easily be modified if you knew what you were doing. I bought
one along and acquired a list of the required modifications.
The modifications added an additional 40 channels (unauthorized) and
increased the carrier power from 5 watts to 15 watts.
It also increased the effective single sideband mode power to
over 30 watts depending on how much you modulated it which was
also another "tweak". At the time we lived in a rented house
near the shore and on Sunday mornings I could communicate via "skip"
with people in much of eastern Europe, as far away as Italy. In the
evening I could easily talk to people west of the Mississippi using
skip as far away as California, depending on the time as the sun set.
Ended up doing the same mods for a couple of people who also
bought the same Radio Shack radio.
Don't know whatever happened to that radio. I lost interest in CB
after a while.
Keyser Soze
phone that much. :)
Mr. Luddite
communications and people like me who were more interested in
seeing how far you could communicate with others, similar to
HAM radio and their custom of exchanging "QSL" cards by mail confirming
successful contacts.
Only time I was glad to have a CB radio in my vehicle was before
cell phones came along. Was traveling up Rt. 95 from Long Island
heading home at about one in the morning. It was raining hard
and a car whizzed by me in the fast lane. Suddenly, all I saw
were his headlights flashing back at me several times. As I
approached him, his car was upside down on the side of the road.
He had hit a large puddle of water and had hydroplaned, causing
his car to hit the center guardrail and then flip several times.
Got on the CB and after a few tries contacted someone who called
the state police. I helped get the guy out of his car and he
sat with me in mine until the police arrived. He was shaken up
big time but didn't appear to have any serious injuries.
John H.
and NV. Depended on my CB to keep me awake during the drives to and from these units. Wonder if the
truckers still use them much. My wife depends on an app called WAZE, which notifies of accidents,
cops, obstructions, etc, and suggests a route around the problem. I don't trust it much, but it's
all she uses.
John H.
CBs also. Don't know about now.
Mr. Luddite
Denver CO to pick up a '55 Ford F-100. I had the Ford 350 diesel then,
bought a car trailer and headed west. It was a great trip and I was
alone. Just me and the road.
I stopped at a truck stop somewhere along the way and decided to buy a
CB radio and installed it.
It became useful as I got further west on the highway when I'd drive for
miles without seeing another vehicle. After I picked up the '55 Ford
it was fun talking to truckers on the way back to MA when they saw
the F-100 on the trailer and were commenting to other truckers about it.
I'd join the conversation and it killed a lot of time driving back home.
Once I got back though I ended up taking the radio out and giving it to
one of my grandsons to play with.
John H.
one in the truck.
Bill
Would be nice to know what is coming.
waynebatr...@hotmail.com
These days everyone has emergency communications via cell phone. It's
much more reliable and easy to use. Ham radio is also experiencing a
decline in popularity as the internet and sat phones have made it easy
to communicate all over the world.
---
This email has been checked for viruses by AVG.
https://www.avg.com
waynebatr...@hotmail.com
We use both AIS and radar in situations like that. Of course they're
very useful at night also.
Mr. Luddite
reliable communications. The challenge was in frequency selection,
antenna placement, etc. just to see how far you could establish
communications. Kinda a nerdy hobby I guess.
Even in the Navy on one of the ships I was assigned to and before it's
homeport was changed from Newport, RI to Naples, Italy we used to
try to maintain comms with another ship using the least amount of
transmitter power as possible. Best we did was a two-way FSK teletype
connection off the coast of RI to another ship transiting through
the Straights of Gibraltar using less than 1,000 watts.
Mr. Luddite
Charleston, SC. and have set up for the winter. This is their first
voyage after all the work they did on the boat and it looks like they
are enjoying the adventure big time. They *did* stop at Coinjock to
sample the fare and only ran aground once on the ICW on the way down. :-)
gfre...@aol.com
station with an illegal antenna (too tall) could reach 15-20 miles
down the bay. If you had a decent marine antenna they could hear your
answer.
Most of my time was talking to truckers tho. I did make some pretty
good friends over the years.
Its Me
Ham operators are still pretty useful in certain situations, especially when the cellular system is down. Fo example, there's a privately owned (by ham clubs) radio network that covers the Carolina's, and up into Virginia and part of Georgia. With a ham license and a $400 handheld, you can talk to another ham anywhere in that area. That's not an unusual thing.
John H.
approaching from the east side on I-10. We were both on high ground with the valley between us and
were over 30 miles apart.
waynebatr...@hotmail.com
Good for them. If you've never touched bottom on the ICW, then you
just haven't been at it long enough. There are some real problem
areas that are only negotiable at half tide or better, other places
that have missing navigation marks, and a few spots that are badly
charted. We are fortunate to have a full length keel with a metal
shoe on it so the props and shafts are well protected.
Charleston is not nearly far enough south for a comfortable winter on
a boat however. We have neighbors down the street that just brought
their 58 footer down here from the Charleston area.
gfre...@aol.com
saved a guy one night. Then I was one of the guys and got to know a
couple dozen who were regulars there in the middle of the night. I was
really surprised how many just had a route they ran over and over
again. It really would bore me to death after a while but these guys
just said it was a job, like driving a bus. The regulars all seemed to
know each other.
They did tip me off on the best times to travel I-95 and the best way
to get to I-75. They also helped me make some real fast trips, like
Clinton to St Pete in 14 hours flat. I was in the "rocking chair" most
of the way.
Mr. Luddite
something further south ... like in Florida ... but everything was
booked for a boat their size and draft. They both travel throughout the
USA and Europe on a regular basis so the boat is just a temporary place
to stay.
gfre...@aol.com
I doubt I will see that much ship traffic in the Estero Bay anyway,
unless they can run in 2-3' of water.
We have been socked in with fog tho. My wife thought it was so cool. I
was navigating with aerial photos, a compass and the shapes of the
edges of the mangroves.
We did fine.
gfre...@aol.com
were already migrating to digital, hooking ASR33s (teletype) to their
ham gear. Some still worked 2 meter radio telephone but not that much.
The guy from Ft Myers who retired in Tennessee says they have a pretty
active ham group there but they are connecting up PCs.
I guess ham has become just an RF modem.
Mr. Luddite
They grabbed me because as a former Radioman who had attended Teletype
repair school they wanted to get an old send/receive teletype machine up
and running to use it with the ham gear. I finally found enough parts
to get it running but then had to convert it to 60 wpm to make
it compatible with civilian teletypes. I did that sorta as a side job
as most of my time on duty was spent relaying voice messages to service
members families.
gfre...@aol.com
On Wed, 28 Nov 2018 15:44:13 -0500, John H. <salmo...@gmail.com>
than I thought on the Chesapeake. The base was a Schiebels on the
Potomac, north of Point Lookout and we used to fish that ridge that
you see on GE south of Tangier Island. Usually we were shaky getting
them all the way down there but we were usually OK by the time we got
to TI.
We could always raise the Bay Queen, the head boat out of Schiebels. I
think they may have had a foot warmer on that boat tho. The antenna
was also 30' above the water. They were in constant contact with the
base.
Everyone used obscure references on the radio so as to not give away
all of the fishing spots. ;-)
I am not sure we ever fished anything except that ridge, that was not
that well known ... before GE anyway. This is the first time I noticed
it but I know that is where we went.
gfre...@aol.com
in the MARS program. He got out of the AF and went to work with Univac
and gave me a bunch of MARS stuff he had accumulated. I still have
most of a 2000' spool of 30 ga wire. The 10 feet at a time I use every
few months has not even made a dent in it.
Bill
there a long time. Was surprised at all the cool stuff that migrated
there.
Bill
platform. As to radar, I screwed up about 50 years ago, not getting a
license with radar endorsement. Friend took care of the police radars,
great side business. I spent 3 years fixing airborne transport radars.
gfre...@aol.com
calibrating them I imagine they get thrown away if they break.
Electronics these days doesn't really break that much ... why I
retired.
waynebatr...@hotmail.com
>IBM collected a lot of hams. Back in the days when I was in DC they
>were already migrating to digital, hooking ASR33s (teletype) to their
>ham gear. Some still worked 2 meter radio telephone but not that much.
>The guy from Ft Myers who retired in Tennessee says they have a pretty
>active ham group there but they are connecting up PCs.
>I guess ham has become just an RF modem.
Digital comms is sort of on the cutting edge of ham technology these
days although it goes back more than 15 years at this point. There is
a device called a Pactor modem which acts as a combination modem and
packet encoder. It attaches to either a ham rig or commercial marine
tranciever, and allows error free transmission at speeds up to 4800
baud under good conditions. It's fairly sophisticated in its
operation, automatically adjusting speed and re-transmissions based on
radio conditions and error rates. I use it when we are cruising in
the boondocks for EMAIL, weather, stock market quotes, etc.
<http://www.docksideradio.com/ptcii.htm>
gfre...@aol.com
wrote:
from home. As long as you were just using text and maybe some low
resolution pictures it worked great.
When the V.32bis (~14.4Kbps) and V.34 (19.2Kbps) stuff showed up we
were awed.
I am surprised they can't get that trellis modulation stuff running on
RF. We were doing it on nasty dial up lines at 2400 baud. (not the
same as bps)
The baud is 2400 (basically the frequency of the carrier and about all
dial up can deal with) They then pick off 8 data bits from every wave.
(19.2)
4800 bps is only looking for a bit at each peak. (2x baud). Maybe RF
can't beat unshielded copper.
They get away with higher rates by using better error correction
algorithms. A clean line will run at the rated speed and it starts
falling off fast from there. At a certain point the modem will kick
down to a lower speed until it finds one that works. That sounds like
what you have too.
Cool stuff tho until they get the couple hundred satellites they want
up for broadband connections.
John H.
Its Me
Bill
as a side job.
waynebatr...@hotmail.com
The Pactor speeds are limited by FCC regulations designed to minimize
bandwidth and adjacent frequency interference. Of couse HF SSB is
also much noisier and susceptible to fading than a telco landline. The
automatic re-transmission of error packets and adaptive signaling is
very cool however, and quite useful for short messages, weather data,
etc.
gfre...@aol.com
correction that will plug in a couple of missing bits most of the
time. It has been a while (almost 30 years) but I think you lose a
byte or two overhead in a packet but it can correct 1 or 2 bad bits.
It was pretty much just magic for us since it was a chip buried in the
hardware.
As long as they don't go nuts with the graphics and multimedia 4800
bps is plenty