Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: Prev 1 [2] 3 4 Next   Go Down
  Print  
Author Topic: Which AM Transmitter?  (Read 38227 times)
N2EY
Member

Posts: 5079




Ignore
« Reply #15 on: October 03, 2011, 09:15:01 AM »

Are all AM stations old Boatanchors?

Most are.

Do people do AM with modern rigs?

Yes.

But there are reasons for the prevalence of BAs, GBs and such.

The first reason is that most modern rigs either don't do AM at all, or don't do it all that well. Their receivers aren't optimized for the mode, and their transmitters usually do AM by generating SSB and reinserting the carrier. There are exceptions, of course.

With a BA station, you're not trying to make a fish out of a dog (see Monty Python pet shop sketch). Instead, you start with a rig made for the job. Even better, you can often do a restoration and improvements and have fun in the process.

There are several paths, all with good and bad features:

1) Find a ready-to-go fully-restored AM setup. Expensive but the least work.

2) Find a fixer-upper AM rig and fix it up. Lots of freedom in what you do.

3) Find a rig meant for another purpose (AM BC tx, military surplus, etc.) and convert it to ham use. Usually good for only a few bands, but what an experience!

4) Homebrew from scratch. Most freedom, most work.

Remember we're talking RX as well as TX. All sorts of combinations possible; you might get a fully restored rx (National 303, anyone?) and pair it with a basket-case Ranger you restored, driving a home-brew final and modulator. The possibilities are endless, from PW little rigs to a full-limit rig taking up a couple of racks. (Why limit yourself to one?)

73 de Jim, N2EY
Logged
N2EY
Member

Posts: 5079




Ignore
« Reply #16 on: October 03, 2011, 09:32:41 AM »

If you've won the lottery and want an AM rig, then a 32V1 or 2 from Collins or even a KW1(?) - the rig with a pair of 4-250A in the PA and 872 rectifiers. I seem to remember they were priced in the thousands of dollars in the early 1950s...and you need a 75A2 to go with it.

Historical note:

AFAIK there were only two plate-modulated AM amateur transmitters ever made which ran the old USA 1000 watt DC input legal limit.

The first was the Johnson Desk Kilowatt, which cost $1700 back in the 1950s - without the rest of the desk and without the driver! (The Ranger was the usual driver for AM and CW, the Pacemaker for SSB...)

The second was the Collins KW-1. Don't know what a KW-1 cost new back in the day but I know they were in the "if you have to ask, you can't afford it" class. Only made for a short time in the early 1950s as Collins soon went for SSB with the KWS-1 and 75A-4 pair, then the S-line.

There were other rigs which ran hundreds of watts on AM (Johnson Five Hundred, Globe King, Johnson Thunderbolt as AM linear, etc.) but for a full gallon of plate-modulated AM there were only the two above that I know of - plus homebrew, converted surplus, and rigs made for commercial service.

One major reason some hams resisted the move to AM so strongly was the enormous investment they had in high power AM. Who can blame them - particularly if the investment was in the form of a homebrew rig built up over many years, hours and dollars?

73 de Jim,, N2EY
Logged
G3RZP
Member

Posts: 1265




Ignore
« Reply #17 on: October 03, 2011, 11:29:49 AM »

ARRL Handbook, 1953, Catalogue section.

Collins KW1 $3850
32V-3, 150 W CW input, 120 W phone input $775
75A3 Rx, 3 kc/s mechanical filter $530
1kc mechanical filter $75
10 inch speaker $20
crystal calibrator $25
NBFM adaptor $22.50
Hallicrafters SX73 $975 S38C $49.50 T20 transmitter '100 watt AM phone output', crystal controlled, $449.50

National HRO 60 $483.50 less speaker, slightly higher west of Rockies(!)

Johnson Viking II, as a kit, crystal controlled, $279.50  VFO kit  $42.75.

No Heathkit transmitters or ham band receivers. (that must cheer AC5UP!)


So much is $4500 1953 dollars today? (KW 1, 75A3, 1kc/s filter. speaker and crystal calibrator)

Globes Scout, (World Radio Labs, Council Bluffs, IA) 50 watts, crystal controlled, $99.95. Globe Champion, again xtal control, 165 watts, $349.50

ARRL membership and QST. $4.00. ARRL Handbook $3.

I wouldn't be surprised if a working KW1 wasn't fetching $3850 today.
Logged
AC5UP
Member

Posts: 4546




Ignore
« Reply #18 on: October 03, 2011, 01:02:57 PM »

(that must cheer AC5UP!)

But it does explain some of the popularity of Heathshkit in the late 50's and early 60's... By designing around the plethora of surplus parts on the market at the time, the mystical lure of the kit building experience, and the alleged advantages of Benton Harbor Engineering Excellence...  Roll Eyes Heathshkit could compete effectively on price.

All I know is that my father bought a brand new 1950 Chevrolet DeLuxe Coupe with a straight six under the hood and three on the tree for $1,895.00 plus tax.

Translation: The Collins KW1 quoted above was approximately equal in cost to two Chevy's or maybe one Cadillac, +/- power windows, automatic transmission and undercoating. If I was buying a KW1 I'd definitely want it undercoated.
Logged

N4NYY
Member

Posts: 5224




Ignore
« Reply #19 on: October 03, 2011, 03:19:58 PM »

Quote
Johnson Viking II, as a kit, crystal controlled, $279.50  VFO kit  $42.75.

I actually had one to restore, but ran into a major snag. Several of the front pots/switches, were rusted in by an apparent water leak. Essentially, it killed my ability to removed them and removed the front face. Because I would have to destroy a couple of the knobs.

So I started to part it out, and used that money to fund other radio projects. I got some good money for the parts. I still have some left. Believe it or not, one knob still refused to come off. And I am trying not to ruin the face trying to get it off.

It is a shame, as it would have been nice to restore it.
Logged
N2EY
Member

Posts: 5079




Ignore
« Reply #20 on: October 03, 2011, 04:02:31 PM »

So much is $4500 1953 dollars today? (KW 1, 75A3, 1kc/s filter. speaker and crystal calibrator)

That's easy!

Per the Westegg Inflation Calculator:

http://www.westegg.com/inflation/

$4500 in 1953 equates to $36,258.07 in 2010. (The calculator works up to the end of the previous year)

As I wrote before - if you have to ask, you can't afford it.

Note how much of the price is for the transmitter, too.

I wouldn't be surprised if a working KW1 wasn't fetching $3850 today.

I'd be surprised if you could find one in working order priced that low. There were rather few of them made, too, so just finding one for any price isn't easy.

73 de Jim, N2EY
Logged
AC5UP
Member

Posts: 4546




Ignore
« Reply #21 on: October 03, 2011, 04:08:21 PM »

$4500 in 1953 equates to $36,258.07 in 2010. (The calculator works up to the end of the previous year)

Which makes me wonder, had a person bought $4,500 worth of IBM, GM, ESSO, ALCOA, etc. in 1953 what would it...............................

All I know is that if I had bought $4,500 worth of Microsoft in 1983 (and I could have) I wouldn't have any money worries today.

Now I'm depressed. Thanks, guys!
Logged

N2EY
Member

Posts: 5079




Ignore
« Reply #22 on: October 03, 2011, 06:10:41 PM »

Which makes me wonder, had a person bought $4,500 worth of IBM, GM, ESSO, ALCOA, etc. in 1953 what would it...............................

All I know is that if I had bought $4,500 worth of Microsoft in 1983 (and I could have) I wouldn't have any money worries today.

Hindsight is 20-20.

Whenever I get to thinking about those sorts of what-ifs, I remind myself of the folks who bought Enron or similar stocks...

People remember the successes but forget the failures.

Predicting the future is a good way to be embarrassed. I remember seeing the movie "2001: A Space Odyssey" when it came out in the 1960s. That film predicted the following for the year 2001:

- an orbiting commercial space station
- commercial shuttles to low earth orbit, run by Pan Am
- Permanent bases on the Moon, some run by the USSR, some by the USA, others by China.
- Orbiting nuclear weapons platforms
- Picture phone service brought to you by The Bell System
- Sentient computers
- Manned missions to Jupiter

And much more. OTOH, PCs, theinternet, cell phones, the breakup of the Soviet Union and much more were not foreseen at all.

Now it's ten years past 2001, and the only thing they predicted that has come to pass is the picture phone - in the form of Skype, which costs nothing.

Go figure.

73 de Jim, N2EY

Logged
N4NYY
Member

Posts: 5224




Ignore
« Reply #23 on: October 03, 2011, 07:01:46 PM »

Quote
Whenever I get to thinking about those sorts of what-ifs, I remind myself of the folks who bought Enron or similar stocks...

http://www.ebay.com/sch/i.html?_nkw=enron+stock+certificate&_sacat=0&_odkw=enron+stock&_osacat=0&_trksid=p3286.c0.m270.l1313

Logged
G3RZP
Member

Posts: 1265




Ignore
« Reply #24 on: October 04, 2011, 02:26:52 AM »

A good investment in the 1960s would have been some of the WW2 surplus radio kit. A transceiver that could be picked up for about £3 then will, if in good condition, fetch about £350 now. I saw a TCS pair - rx and tx - go for over £400 - $650. That was at a private auction, so heaven only knows what eBay would have got.
Logged
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #25 on: October 04, 2011, 07:07:26 AM »

The problem with most plate modulated AM amateur rigs is they are plate modulated beam tetrodes.

That means the tubes cannot be plate modulated, because they have constant current with varying anode voltage. The best we can do with plate modulation on tetrodes or pentodes or beam tetrodes is around 50% modulation before severe distortion sets in.

We have to do a combination of efficiency modulation and plate modulation to get good audio, and that means either modulating a grid along with the plate or an earlier stage along with the PA. The Johnson Ranger for example has 100% negative peaks with about 50 volts positive on the anode supply, because it is really combo screen and plate modulation.

http://www.w8ji.com/amplitude_modulation.htm


I get a kick out of reading boatanchor audio websites where people at negative limiting by stopping an anode supply from going negative with a diode and think they won't splatter.

They add negative feedback within the audio stages and remove driver transformers while the THD of the modulation system is 10% or more because of the modulated PA stage non-linearity in response to modulated voltage.

These are cheap Ham rigs that served a good purpose in their day. It didn't matter in the 1950's if they were -25 dB 10 kHz out on each side because no one had good receivers anyway.  :-)
Logged
G3RZP
Member

Posts: 1265




Ignore
« Reply #26 on: October 04, 2011, 07:39:13 AM »

One trick my father found useful and thought he was being inventive was a capacitor across the screen dropper resistor from the modulated B+ to increase the amount of screen modulation. He thought he was being inventive but it was a technique originally used, I found, by RCA in the early 1930s......

An interesting point is suppressor grid modulation. It seems to me that on the negative cycles of audio, you will start diverting a substantial amount of current to the screen. That suggests that there needs to be a series resistance to the supply if there isn't going to be over dissipation in the screen grid, and that as a result, screen volts will drop on negative half cycles, increasing the modulation depth on the negative half cycles, but not the positive.

A separate winding on the modulation transformer works well, too. I saw that technique as an apprentice on a BC tx. The modulation transformer weighed 14 British tons (2240 pounds), and was wheeled in by a gang of labourers.....3 vapour cooled PA tubes in Class D, 750kW carrier. That was QRO!
Logged
AC5UP
Member

Posts: 4546




Ignore
« Reply #27 on: October 04, 2011, 08:01:14 AM »

That was QRO!

http://hawkins.pair.com/wlwmanual/wlwman11.jpg

Seymour at: http://hawkins.pair.com/wlw500kpics.shtml
Logged

G3RZP
Member

Posts: 1265




Ignore
« Reply #28 on: October 04, 2011, 08:44:57 AM »

And these days, I'm a professional QRPPPer! Allowed a maximum radiated power at 25 microwatts, and usually attaining about 50 nanowatts - from a transceiver in a pacemaker.
Logged
KA5N
Member

Posts: 4380




Ignore
« Reply #29 on: October 04, 2011, 08:55:30 AM »

The last KW-1 I saw for sale was priced at $6000 so compared to 1953 price a  KW-1
is a bargain today!!!  Of course the problem would be finding one.  Probably do better finding an old junk Gates broadcast transmitter (or similar) and changing out the tank circuit.

Allen
Logged
Pages: Prev 1 [2] 3 4 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!