I cannot recall what LMO stands
for? Maybe Local Modulated Oscillator?
Linear Master Oscillator
I have the same phenomenon with the 872's or 575's (whichever happen to be
installed) in a homebrew rig. 3 light but one is dark, and the phenomenon
stays at that socket. No obvious other issues.. how curious.
Make sure the tube filament pins are making good contact. I have seen it
fail
3B28's have a sort of white glow in the gas, right?
Usually the is no immediately visible glow at all. If you carefully peer
down inside the plate/filament structure, you will see a dim violet glow.
You may have to turn off the lights to notice it.
Don k4kyv
FT-243 xtals should work ok. The BC-610 was designed just before WW2. At
that time xtals usually came in a round holder about the size of a
half-dollar, with two pins that fit into a standard 5-pin tube socket (the
pin spacing was not the same as that of the BC-610 xtals, though). I think
Best part is, the later ARC-5 modulator is actually plate modulated. A
few folks have complete, working stations on the air, not sure if any
are currently checking into the weekend Military net early Saturday
mornings.
My first homebrew modulator, in early 1960, used the modulation
Anybody know where I could find a schematic for these amplifiers?
Whats the best way to build a 1kw (capable) modulation transformer to plate
modulate an amp like these? Not that I'd want to. Just asking...
You would want to rewire the amp from grounded grid to grid driven, and
convert the
Geoff wrote:
I spoke up (I'm not shy!) and said What's the matter, this stuff boring
you? HE said Hell yeah! I don't come turn my radio on to just sit
and listen to all this electronic building crap! I wanna talk about
what's important to ME!
Typical SSB appliance operator
I was going up and down streets power pole to power pole on my bicycle with
a AM Walkman radio tuned to 540 and 1700 Khz.
I use a Radio Shack aircraft receiver. About the size of a HT, and makes a
nice line noise sniffer. The bicycly is a good idea also, since every
vehicle we have here,
You might be able to use a pair of 838's or 805's in place of the 203A's.
The 838's have the same pin connections, while the 805's bring the plate
lead out of a plate cap on top of the tube; otherwise they are essentially
the same tube, with the same filament current as the 203A. The 838
Agreed Mike. I had a power company lineman tell me not to do the
sledgehammer trick. If something is about to break, it could fall with
some consequences.
If the pole has a guy cable, just give it a good yank.
Interestingly, if the AM
signal, with or without carrier, is multiplied at the receiver with
a regenerated carrier of proper frequency and phase, then the
baseband modulating signal is recovered.
That's why it is called a product detector.
My Collins 20V-3 has those dropping resistors as well. Seems like the
experts blew this one.
Oh, well, not everyone can be perfect.
Actually, the 120 volt bulbs with dropping resistors should last longer.
The series resistance will buffer the inrush current. The cold filament of
an
From the beginnings of radiotelephony there has been a question whether
sidebands exist as physical reality or only in the mathematics of modulation
theory. In the early 20's this was a hotly debated topic, with a noted
group of British engineers maintaining that sidebands existed only in
The Part 15 label pretty well says it. Part 15 devices must not cause
harmful interference to licensed services and must accept any harmful
interference from licensed transmitters. They operate entirely on a
secondary, provisional basis. They enjoy no legal protection whatever from
duly
I have noticed that many radiating consumer devices, namely Chinese-made
touch lamps, do not carry any kind of Part 15 warning label. It's been my
experience that those things are terrible about polluting the spectrum, but
little seems to have been done about it. I may be experiencing that
I don't believe that the carrier still exists because of tank circuit
ringing when 100% negative modulation is reached either. The Q of the tank
only allows for a couple of cycles at most when no carrier is present. It
decays very quickly. With modulation, even at voice frequencies, the
Don't let a bandwagon get rolling that touts rf-polluting touch lamps as an
essential convenience for seniors.
http://www.qrz.com/ib-bin/ikonboard.cgi?s=4f1c5ce63cdcc1d9760d46baa0e06e61;act=ST;f=7;t=80255;r=1
I am nearing completion of my 20V-3 for 75M and was wondering what VFO's
are available that easily interface with the 20V-3.
The 1.5-3.0 mHz PTO unit from a T-195 or T-368 would work. I use a modified
T-368 PTO/exciter unit as an all- band VFO unit. With the bare PTO, you
will need to
I'll take a very wild stab at it. From the RCA TT-4 handbook, the 833's at
3000VDC require 400V peak G-G volts, that is 242 V RMS. The drive is 20W.
That makes the current 82 mA. That makes the impedance 2950 ohms G-G.
If you have an old output transformer such as a 6K CT to 0-4-8-16 ohm
I have a older BC 1F series gates transmitter. I would like to do away
with the 845 driver tubes and drive the 833's with a 100 watt PA amp.
Does anybody have any Ideas what I would need to match the amp to the
driver transformer of the 833's.
Don Moore
W5FFK
Don,
I think you would be making
If you measure current from the filament transformer center tap to ground,
you'll have not only cathode current, but plate current, as well. Just
look
over at the grid current meter, subtract that from the plate meter, and
there's
your plate current, AND it's in a nearly ground potential
What your speaking of Don is shown in the following article.
http://www.qsl.net/wa5bxo/pptriodes/pptriodes.htm
If you measure current from the filament transformer center tap to
ground,
you'll have not only cathode current, but plate current, as well. Just
look
over at the grid current
I first noticed this 24/7 interference a couple of months ago.
The interference covers the entire HF spectrum - from 80m to 30 mHz. It is
spaced intervals of approximately 30.475 kHz. On an AM detector it sounds
like a tone modulated carrier, but careful observation shows that there are
I am in the process of restoring a Johnson Ranger I. I obtained part of
the
manual and a schematic. That's when I noticed that two of the tubes were
missing. The tubes are the 6AL5 bias tube and the 12AU7 keyer tube.
A second question is whether I should refit this old Ranger to bring
I had a problem with a treadmill. Even though it was
not running, if left on it put out junk on 6, 2, and
440. Only solution was to turn power switch off
Wow, they are putting rf generating trash in EVERYTHING. What under the
sun does a treadmill use electronics for? Before we know
Resonance, as I understand it, occurs when the capacitive and
inductive
reactances cancel.
not cancel .. 'are equal'.
R = X(sub L)=X(sub C) or when Reactance is at, or very near 0 (Zero)
Yes, but if they are equal and opposite would they not cancel?
Yes. Inductive reactance
I could not resist.
John, WA5BXO
Could you suscept?
Don, k4kyv
Who publishes the AMRadio Digest and how do you gain access to it?
Don K4KYV
I'm sorry if I'm seeming a little dense, but I can't get unwrapped from the
'single wire fed version' of this antenna.
Open wire output from the link has *2* wires. I can see attaching them to
some
open wire line, and feeding this Wyndom antenna at 1.8125, and having the
antenna resonant on
With BA unit wit Pi networks you don't need a TransMatch (they ARE NOT
antenna tuners). Most will match anything between 50 and about 500 ohms.
One
exception is the Heath DX-60. It is limited to 50 to 75 ohms becase of the
built in LP filter.
You need a resonant antenna for each band you
From: Merz Donald S [EMAIL PROTECTED]
Reply-To: Discussion of AM Radio amradio@mailman.qth.net
To: Bob Macklin
[EMAIL PROTECTED],[EMAIL PROTECTED],'Amradio
(E-mail) amradio@mailman.qth.net
Subject: [AMRadio] RE: GB Antenna Tuner Wonderings
Date: Tue, 14 Dec 2004 11:14:24 -0500
Thanks for
I need a National R 175 RF choke or equivalent. If anyone has one, buy or
trade. This is the plate feed RF choke for RF decks.
73 Jim
W5JO
Do you still need one? I found one in some old junk. I'll never have a use
for it.
73, Don K4KYV
Don,
How did you get your dipole up 110 feet? Is it strung between towers, or
do
you have some gigantic trees in your yard? It took me a long time just to
get mine up 35-40 feet up in my trees using a slingshot-fishing reel combo.
Subject: Re: [AMRadio] Antenna Tuner Wonderings
The
r Nov. I tried to bring
it up today and it requested my username and password. I tried the one I
was issued when I joined the Forum and it does seem to work. Anyone have
an
idea behind what's going on?
Were we issued a password, or were allowed to submit our own? I don't
remember. I used
Then those aren't what we call real hams. I don't think I know of an
AM Radio Operator that would be caught *dead* running a store-bought
dipole antenna. Them folks are no more than an appliance operator.
I get a chuckle when someone tells me they are using a homebrew dipole. I
assume, by
There is already an AM group on approx 14.286. I haven't run 20m AM since
the early 70's. It is OK for one-on-one contacts, but when roundtables
develop, there is the problem of the erormous skip zone on 20. You can
count on one or more members of the roundtable being inaudible, so you
What kind of crappy antennas are you using, i.e., doublets fed with coax,
open wire lines, etc., or end-fed wires? Or, some combination of types
maybe?
Rather that building up a bunch of tuners you might consider putting your
efforts into erecting a set of antennas that all worked
I'm confused on your commentary (The imaginary AM Window is another
thing that needs to go.).
I've heard many AM'ers say that many, many times, and I agree. The vicinity
of 3830 is often unoccupied after primetime hours in the early evening and
the SSB'ers go to bed. Sometimes a few
Looks like the AM Forum site is down. I recall Gary saying they were going
to do some maintenance and possibly go to a new server. All I get when I
click on the site is:
Network Solutions: This site is under construction and coming soon.
No mention of the AM Forum.
Of course, amateurs have for years used pentodes and tetrodes, including
807's and 1625's, as triodes in grounded grid linear service. I have never
seen the resistor used. They simply ground all the grids and feed rf to the
cathodes.
With 1625's and 807's, a modification is required, to
...The EL-34 is inexpensive, readily available, has small diameter (like a
tall 6V6), and has beefy ratings I was actually using a Svetlana EL-34
that cost US $12.00.
Unfortunately, the audiophool community has got in on the action. People
are paying top ridiculous dollar for EL-34's
It doesn't get any better either. With modulation the dissipation does not
decrease even though the efficiency increases at the peak power levels. The
carrier power is still there 100% of the time at 30% efficiency. The audio
is in the form of separate side bands that is additional power that
The original date for Dayton was the 3rd weekend in April. It might have
been snowed on and was often unseasonably cold, but it hardly ever got
rained out. I remember in the mid 70's one of their brochures promoting
the hamfest made it a point to claim that in 22 years, it had been rained
I used to be a phone phreak in my younger days back when the blue box (for
free long distance called) used to work.
The coin sounds in a payphone is called a red box. Doesn't work on COCOT
(customer owned) payphones because the dialtone you hear is not from Ma
Bell's line but generated by
Funny how NPR and the liberal media freaks mentioned in the story can
take
something like a UTE such as a number station and turn it in to a cult! I
remember when I actually liked listening to NPR. Even 'A Prarie Home
Companion'
has gone sour like a bad compost heap. Bummer.
I don't
I've gone so far as to build a part 15 transmitter so I can listen to
streaming internet stations on my old radios.
I have been looking for something that puts a stable, full fidelity stereo
signal on the FM band so I can retransmit streaming audio throughout the
house and pick it up on
NPR is pretty mainstream now after the goivernment cut
the legs out from under them.
The corporate sponsor notices on there are starting to
sound more and more like commercials all the time, he he!
Even more so with public TV. Some of those sponsor notices are nothing
but downright
I thought you would be interested in this story that appeared on NPR's All
Things Considered today, NPR : Music by the Numbers
http://www.npr.org/rundowns/segment.php?wfId=4167689
To listen to this story, click on the headline to the story using a
RealAudio or WindowsMedia player.
what frequencies are these heard on? AM? anything else?
Both AM and CW. Thourghout the shortwave spectrum. It's been a mystery for
nearly three decades.
I am only the messenger, in case someone is interested. Do not call me.
Contact Theo, N8CSU @ (865) 925 1290.
Pair of 805's modulated by another pair of 805's, 250 watts. Built circa
1945. Custom-built by a company called ERI; supposedly only three were ever
made and the other two ended up
Years ago I used to use a 100 watt light bulb for dummy load and the rig
was a pair of 807's in the final modulated by another pair. Once I was
testing into the light bulb and when I finished, I listened on the frequency
and heard some hams complaining about that idiot who keeps testing
http://schema.web1000.com/tech.data/6l6.txt
Some good tube theory with a twist towards Guitar amp needs:
http://schema.web1000.com/tech.data/AXTheory.pdf
---
When I tried either link the URL suddenly flipped and I got
PaysForSurveys.com. Even tried typing it in and same thing
The 837 WAS an option with that amplifier. I recall a friend of mine bought
one of those amps to run AM. He planned to drive it with an Eico 720, plate
modulated. Not understanding the principles of low-level modulation, he
thought he could amplify the 40 watts or so output from the Eico
Run the filaments for a minimum of half hour before applying high voltage.
You don't mention what tube you are speaking about, but if it is an Eimac,
go to their website and read their technical information.
http://www.cpii.com/eimac/index.html
The information is good no matter who made
The 450th is a big triode, so I dont think you can run it single ended pie
net output, you would need to do 2 250th tubes in push pull or something,
but the 450th would do the cathode modulator quite well.
You could use a single-ended pi-network type output circuit, with a balanced
grid
the BC250L's grid/driver plate
coil is NOT on a bakelite form. It is a ceramic one, 2 1/2 inches in
diameter.
I still get the exact same grid drive on 160 meters as I did on the
broadcast
band. My problem still remains efficiency, and maybe I'll just have to
settle
with 61% and be happy.
I moved my BC1-T from 1230 kc to 160m, by proportionally scaling back the
fixed capacitances in the PA tank circuit (both loading and plate tuning
caps), readjusting the rotary and fixed inductors, and getting the grid
drive up to normal, and efficiency is about the same or better than it
By 'tilt' I mean the observable tilting of the top and bottom of a
square wave (or resulting modulated envelope) caused by low frequency
roll off and non constant group delay through the transmitter in
question.
That's why the transmitter frequency response, including transformers,
should
I have always admired what Don has done with his modulation system. That
3400 hertz brick wall filter is a rarity unless one uses high technology
active circuitry such as active op-amps, switched capacitor filters, dsp,
etc. I believe Don has a passive module that does a great job. I wonder
What about bandwidth? +/- 5kc would be a 10 kc band width. I thought we
were supposed to limit our band width to 6kc. Please correct me if I am
wrong.
That is a popular urban myth. There is NOTHING in the US regulations that
specifically limits bandwidth. The regulations specify good
Yes, but there are practical issues. This is certainly not a speedy method.
Changing tubes out of a working rig puts a good tube in jeopardy of a
mis-handling accident. How are results interpreted for a single tube
changed into a push-pull final? You have to keep a different transmitter
Thank you to everyone who responded via postings and private e-mails.
... He mentioned
that he had a 20-foot shipping container's worth of the equipment
sitting in his warehouse, the business owner would love to get rid of!
...
He is planning to move to Eastern Tennessee in the not too
DO NOT
discard the crystals. Someone will purchase the crystals since it is
a CONELRAD frequency.
Why would anyone be interested in CONELRAD crystals? That was phased out
decades ago.
Don K4KYV
_
On the road to retirement?
Of course, we know that running voltages that are too high will kill
the
life expectancy of the tube, by why is running too little voltage bad
for the
tube, if it's developing full emmission at a lower voltage?
If the lower filament voltage does not affect the emission of the cathode
I've got a small variac now on the filaments of my 250TH's, and always
run a variac on the plate transformer primary. But, just to test the tubes
in the final, I reduced the filament variac down to where the 5v meter was
showing around 3.5v, before any emmission was lost in the 250TH's in
the
9 KHZ seems like more than enough for AM, after all, broadcasters are
spaced 10KHz apart, and have very good quality signals...So, a 9 KHz limit
would make some sense, and should be plenty. This is not about broadcasting
or demanding telephone-quality, and what I am saying that I would not
A while back, you said something about running too little voltage on the
older
big jugs, like 833's, 250THs, 4-1000's, etc...
Of course, we know that running voltages that are too high will kill the
life
expectancy of the tube, by why is running too little voltage bad for the
tube,
if it's
,
How long will it be before the govt' adds interface devices to the BPL
home internet connection to further invade in on our privacy. I feel very
uncomfortable with potential broadband utility monitoring of my electric
meter! It opens the door to much invasion.
The first line of defence will
That's odd, I thought the Chairman and three of the five commissioners were
appointed by Bush.
Does it really make any difference? I recall the days when the FCC was
releasing anti-AM rulemaking dockets almost monthly during the 70's and
80's, that the same old crap persisted through the
Take a look at this incredible Rube Goldberg Contraption! Click on BPL
Hi-Res for close-up photos. Note the electrical tape on the low voltage
side. This junk even beats some ham installations I have seen.
http://www.danielwoodie.com/BPLLORES.htm
Actually this provides additional advantages to the Utility Companies
even if you don't subscribe to the internet service. A modem could be
hung on your electric, gas, or water meters, plugged into an AC outlet,
and now all meter readings could be done back at their facilities via the
BPL
I am currently gathering parts for a synthesized DDS VFO as per the James
Hagerty Wa1FFL design. ...
Sure looking forward to getting away from drifting VFO's, or being
rock-bound.
I have a DDS VFO made by SS Engineering. Picked mine up at a close-out
sale at Dayton one year for less than
Has anyone heard of a scam where a person supposedily has a check from
someone in the States that owes him money and he wants you to cash this
check and take out the money for the radio. You then send him the
differerence to him. Sounds like a scam to me.
No way! I'd let him cash his own
I received a telephone call this morning from a lady who told me she was
doing a followup to a PCB inspection at the radio station that gave me the
Gates BC1-T broadcast transmitter about a year ago. She explained that the
station personnel gave her my name as the person receiving the
Any one out there got comments on the Comdel speech processor
They work on AM as well as SSB. I built a homebrew version back it the late
70's using a set of 64 kHz mechanical filters removed from telephone
multiplexing equipment. Mine had better audio quality than the original
Comdel
From: Brian Carling [EMAIL PROTECTED]
... There is a rapid expansion taking
place in the digital sub-bands below 3700 kHz and there
are still many CW ops using the spectrum around 3700 to 3725...
ARRL is VERY interested in promoting digital modes. Sadly the
main one they are promoting is
From: Merz Donald S [EMAIL PROTECTED]
Last Sunday June 6th was the Breezeshooter's Hamfest at the Butler County
Fairgrounds, roughly an hour outside of Pittsburgh. There are only 2
hamfests in Western PA that could be considered medium to large and this is
one of them. The number of
This is a reminder that the comment deadline for FCC Docket 04-140 is
rapidly approaching. The comment deadline is 15 June and reply comment
deadline is 30 June.
Amongst other things, the FCC is seeking comments on whether to adopt the
ARRL's proposed phone band expansion, refarming the
if that is a moduation reactor, you indeed have a treasure. They are
exceedingly hard to find. Typically they are nothing but a huge choke,
30-50 hy's, 1 amp or greater for current. You can put them in the secondary
of your modulation transformer along with a oil filled capacitor and take
the
I could'nt find any info on the 8062 in the UTC catalogs on line. I'll
just
have to keep looking.
I thought you said it was a Chicago Transformer unit.
_
Watch LIVE baseball games on your computer with MLB.TV, included with
I was unable to make it this year, due to time factor. Wonder how the AM
forum went? I recall last year attendance was down. Was it even lower this
year?
It used to never get rained out, back when they held it the 3rd weekend in
April. Then someone got the brilliant idea of moving it
Because of the length and complexity of the latest FCC restructuring
proposal, it may not be immediately obvious when first reading the
document that THE FCC IS PROPOSING TO ADD ONLY 25 kHz to our
existing 75/80m phone privileges, as petitioned by ARRL.
We are all aware of the overcrowding of
It is a good idea to
provide a load for the modulation circuit after the final has reached
below the zero plate voltage point on the negative peaks of the audio
cycle. This can be done with a single HV diode in series with a
resistor of the same resistance as Ep/Ip. This series network is
If a low-pass filter is used after the series-diode clipper, the filter
itself will generate phase shift distortion, resulting in a tilt in the
waveform. A simple pi section (constant-K) filter produces less phase shift,
but the rolloff may not be sufficient to reduce the splatter to an
Sounds like the old Ultramodulation circuit, that first appeared in QST in
1956. I tried it years ago (using 866A's and 200-watt power resistors) but
about the only thing it increased on the receiving end was distortion.
Listeners told me the audio didn't sound any louder or more
I put my plate current meter from filament transformer midtap to ground. I
return the grid bias supply/grid leak to the filament transformer. That
way, the plate current meter reads plate current only and the grid current
meter reads only grid current. I use a pushpull final with separate
Corrections:
I use a pushpull final with separate grid and plate current meters FOR
EACH TUBE, so this requires two separate grid leaks, one for each tube, a
separate protective bias supply for each tube, and of course, a separate
filament transformer for each tube.
I never liked putting
they work well,
but there is loss in the variacs, more sag under load
than without one.
I think part of the reason is the carbon brush contact. You cannot use a
metal contact because it would short out adjacent turns as the variac is
rotated and overheat the coil and burn up the contacts
From: David Knepper [EMAIL PROTECTED]
I have been notified by Advanced Optics Ltd. - these are the folks that
manufacture the Collins reproductions items - that they now have a firm
price on the diamond emblems that mount on the National speakers, etc. For
your information, the emblem that
Was it you, Don, who also said (at one time) that running too little of
voltage
on filaments can have the same undesireable effect on tube life?
That's right. The manufacturers say the filaments need to be within 5% of
the nominal value. I think the story of the 6C21 is that they
The specs are not much different than the 450TL. I've used the 450TL and
6C21 interchangeably in the same rig.
The tube has an oddball filament voltage something like 8.1 volts. The
Eimac spec sheet says that it was designed for radar pulse modulator
service. I once read somewhere that
Collins runs them at over 700 volts in class C plate
modulated service (32V series).
If they don't arc over, and you don't exceed the plate dissipation,
what would be the problem?
That's a good point. I recall an article pre-WW2 in QST which described
getting high peak audio power from
The Astatic Knight Eagle has all of the features of the Silver Eagle with a
unique new finish. The main mic body is done in a luxurious black, while
the
press bar, grip bar, locking clamp, and grille screen are polished and
bright
brass plated. The Night Eagle, also, features an American Eagle
It's far more important to keep the list tidy and useful to all, and the
web lids at bay.
And if you're spending time sifting thru bounced posts, I'd suggest just
letting them fail.
Eventually we'll figure it out when we don't see our posts pop up.
Agreed! I ocasionally hit reply all when
I use an outboard audio amp for my 75A-4 receiver with a system of adaptors
that requires no modification to the receiver itself. I pull audio
directly from the grid pin of the 12AT7 1st audio stage (with the tube
removed). This is a high impedance point, 470k if I recall correctly. To
If anyone would like to suggest we make the list totally open to anyone
without membership, please, let's discuss it
openly on the list for all to see.
Let's leave it like it is. Recall what recently happened to the AM Window
open-without-membership BB.
-k4kyv
BTW, where in 4-land are you where it gets below zero? I thought you folks
had it easy down there compared to those in the great white north? (o:
Here in north middle TN, it normally gets below zero a time or two each
winter, but the last few winters have stayed above zero. The coldest I
Something puzzles me, though - in the listing information it says Features
Thordarson Switchboard Plug-in Terminal Board for quick and accurate
matching of tube loads. Now, I noticed that the terminals didn't have a
typical threaded screw hole or post like most others, but I have no idea
what
Mine is the one with the rounded corners, wrinkle paint on the end bells.
Nice nickel-plated 'acorn' cap nuts on the ends. The openings look too
small for a banana plug but they definitely don't looked threaded either.
What do these push pins look like and does anyone have a picture or know of
What's the OD and length of the pins you need? There's probably something
around that someone will know of that's very close if you can measure the
ones
you've got - when I couldn't find pins for my Johnson swr bridge, it turned
out
that normal bananas with the flat blades removed yielded
201 - 300 of 390 matches
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