The AM Forum

All,

First time on the board and I hope I am in the right place.  I am in the process of constructing a 2 meter AM transceiver, that first appeared in a 1959 issue of Radio-TV Experimenter.  After 51 years of looking at it I decided now is the time to build.  However, in looking at the band plans I see nothing specifically designated for standard AM.  So the question is, on what frequency if any would this device be allowed to operate, so I know it the effort is worth continuing.  Power output is about 3-5 watts max.

Thanks so much and I look forward to any reply.

Tom
KK6XK, Northern CA

You would be allowed (per FCC) to use the rig anywhere between 144.1-148.0 MHz. However, you should consult the band plan, and determine if there is any AM activty or nets in your locality.

Many AM Nets listed at the link below.

http://www.amwindow.org/stuff.htm

Not sure what is going on in six-land, but there is virtually no 2 M AM activity here in the Midwest.  Since the advent of 2 M. FM, most of the 2 M fone activity is on FM.  There is also quite a bit of activity on SSB for weak signal work.  6 M, on the other hand, does still have some AM activity albeit somewhat scarce.  AMers are usually found around 50.4 MHz.

One of the most common rigs that was very popular on 2 M AM back in the 60's was the Heathkit Two'er along with the Sixer on 6M.  Those little rigs were called the "Benton Harbor Lunchboxes" and worked quite well in spite of their low power and rather broad super-regen receivers.  You would be wise to check around your area and see what kind of activity, if any, there might be on 2M AM.  Also, as previously suggested, check out the ARRL band plan for 2M.  You are to be commended anyway for embarking on a home brew project.  Good luck.

73,  Jack, W9GT

Hi Tom, the frequencies I have written down for 2 Meter AM are, 144.400, 144.425, and 144.450MHz.  I don't remember where I found them but I wrote them down just for reference.  I have thought about trying 2 Meter AM but never have.

Al, n7ioh

Tom,

I'm in the Santa Cruz mountains, and have 2meter AM mobile capability, although I'm not sure if I mountaintopped I'd be able to hear you...  50 watts PEP / about 10 AM carrier.

You get it built, I'd be willing to climb a 2500+ foot mountain and give it a shot :)


--Shane

All,

Thanks to all of you for your prompt response and encouragement.  I believe the original 1959 circuit came from C.F. Rockey, W9SCH.  I tried corresponding with him at his QTH in Wisconsin but no response as yet.

I'll investigate those suggested frequencies and try to find a good one.  Looks like if I stay out of everyone else's way it will be OK.

Tom
KK6XK 

The AM calling frequencies vary a bit around the country but most are in the 144.4 to 144.5 range. Ive heard of some at 144.3 but that in the beacon band.

I have 100W carrier from a Clegg Zeus and will have a quad of 17B2's up in warm weather but dont think I can span the continent even to Shane ::)  I also have an old 500W carrier Class C amp and could quickly hook up the PP 8000 modulator.

How about building something for 6M? Thats an easy double hop on Eskip, The Zeus has done that many times there. The calling freq is 50.4

Carl
KM1H

I agree with Carl. Build something AM for 6 meters. For most of 2 meters, the "FM's" and the "diddle-diddles" are the most active. If you build this thing for 2 meters, most likely you'll wind up mostly talking to yourself. The last time I made two 2 meter AM contacts in one day (and they were by prior arrangement) was back in the middle 90's.

Id love to see some real AM activity on 2M with some power. Simple to build these days compared to the 60's...lots of choice tubes and parts.  It needs to start in populated areas such as the Boston to DC corridor and coverage should be better than 75 for many stations using a single or stacked yagis.

Carl

I have a 2M AM/CW HB, rack mounted. Uses a 829B in the final modded by a pair of 807's. I can't swap lanes right now 'cause I have other things in process, but I'd like to get it going. The builder did a great job: i'ts from the late 50's.

Phil

How about 144.107 - 147.973 ;D

If that New York 144.280 net is listed it may be time to remove the listing. Those guys have not been on there for 15 years.

All,

For now I am going with 145.692- AM simplex- it's in the middle of what they call Misc. and Experimental of the ARRL band plan.  Every other frequency seemed to be taken up by pretty specialized assignments.

Anyone see anything wrong with that pick- am I missing anything

Again, the set is going to run about 3-5 watts max.  The receiver is done- when we have the transmitter and PS complete I plan to put it all into an old suitcase and haul it up to the top of Mt. Diablo (about 4,000 MSL in the East Bay- Northern Calif) and see if I can manage a contact with someone.   Since there is a repeater up there running less than a watt that gives full quieting down here it should do something. 

I'd pick something around 144.2, the SSB calling freq..   you'll stand a beter chance of contacting someone than up yahr.

klc

At least down around 144.2 to 144.275, the SSB stations can at least detect that you're there and zero beat. If your receiver has a BFO, you can still copy someone calling you. Horizontal antenna polarization also helps to get the signal out. Above 145 MHz, almost everyone is channelized, antenna vertically polarized, and for the most part, sitting in front of an FM rig.

Gents:

Thanks for the comments and excellent points.  I can pre arrange the initial test.  If it all works out OK, I'll try the lower frequency.

Here in Manchester NH they use 144.450 and there are an assortment of rigs starting to get back on the air. I am in the process of resurrecting and old SCR-522 Transmitter which has been souped up to 15 Watts out and a HB converter on an old ARB receiver.

Mike WU2D

Clegg !

http://oldradioclassified.com/item.htm?nbr=577 (http://oldradioclassified.com/item.htm?nbr=577)

Good case for getting all those shelf queens on the air.
Gorgeous just doesn't get it if you can't use it.
And there is activity if all you metro owners would get them off the shelves.

I use a Clegg Zeus and Interceptor B on 6 and 2M but havent had a 2M QSO in ages, I think there is still a 6AM Sunday group in the Boston area but I could care less at that hour ;D

The new 2M 4 bay array should be up by summer. Not needed for Mike, I can see Manchester from the tower. :D

Carl
KM1H

There was a VHF group around Schenectady NY that was active a couple years back. I could sometimes hear bits and pieces over in VT. Also the group in the Boston metro area, though I was never able to hear them up my way. For a while the 6m band had a lot of AM activity a couple years back when HF band conditions were so crappy at night. I recall K1JJ making multiple references to the gay 6 meter band, PT Cruisers and so on.  ;D

The Clegg gear is sweet to use when you can find someone to talk with. I've used the Venus a number of times on SSB (no AM activity in VT then) and the Interceptor receiver has gotten a lot of use with the Allbander converter for HF listening. Even the 2m CB crowd has thinned quite a bit in recent years. Have yet to use the Zeus on the air, though it is ready to go. Would probably help to have an aerial up for those bands.

Carl, I'm curious what you've found for absolute high power out with yours. Clegg ads in '61 went from claiming 175 to 185 watts of 'talk power' claiming it sounded stronger than many kilowatts. Should be easy enough to drop a 4CX250 in place of the 150 as well for loafing along at full output?

Did manage to snag some spare 7558s at Shelby.

I worked the Albany/Schenectady crowd at 9PM on 6M most evenings when there was no DX worth chasing on the low bands.  When they went off Id swing the 8 el long boom down south a bit and work the guys on LI, NJ, and down to Phillie.

On 2M I could do the same with the stacked 4218XL's but there were very few with anything over 10W and tiny antennas on their roof. Id call CQ and could hear weak carriers with no audio and the only time we could work was during a good tropo lift.

The Zeus will run 125W carrier on 6 and 105-110 on 2M with good tubes. Ive a 250B in there now but there is no difference between a 150A with the low plate and screen voltages available. Im also using Svetlana 572B's in the modulator for the same reason....more plate dissipation overhead for old buzzards.

Im sure with SS in the PS I could pick up a little but 125 to maybe 140-150W aint worth the effort.

Ive done nothing to the audio. Close in contacts say its a little restricted which is what it was designed for. I only run the clipper at part way for long haul and reports are of excellent punch.  One of these days I may change the values and open the response a bit but its not on the priority list.  I remember many Zeus stations in the 60's and the audio was commanding to say the least, and not harsh.

The Interceptor B with the nuvistor front end is hot. The receiver backround noise is so low you would think its dead but then signals just explode in. Clegg took their engineering seriously.

Both units are so stable I can work 6M AM to SSB for long ragchews which I find absolutely amazing. Often they dont even realize Im on AM.

Carl

You are absolutely correct, Marco. SSB is really AM with one sideband and the carrier suppressed. All of those SSB stations are really just transmitting modified AM.  ;D

Carl, after the 80 and 160 aerials are back up in the air (80 this weekend of all goes well), I'm going to get something set up for 6. Would be cool to work you and Pete, Clegg-to-Clegg. WA2PJP also runs this set up from Long Island.

Maybe I'll go Li'l Lulu receiver/transmitter big time this summer on 6.

I was going to do a converter but I actually forgot I had an old R-19 / R508/ARC on the shelf. This is a cute late model 119- 148 MHz command style receiver with 4 mini tubes and 4 loktals and a 12A6 output stage.

It was given to me on a rainy day at Deerfield a while ago. Anyway it is wired for 14VDC and takes 250V. Anyway, I fired it up and it receives 2M AM just fine. I can imagine the NF is a bit high with two PENTODE 9003 RF stages!!! Looks like I have a station of sorts just about ready - a SCR-522 TX and the R508 RX.

Now for an antenna.

Mike WU2D

I finally got a small beam up and worked two 2M AM Stations tonight on 144.450 MHz. The old SCR-522 does over 18 Watts souped up. It uses combination driver and final plate modulation. The Rx is a bit deaf. The R-508 uses a three pentode front end with those half pint sized peanut tubes - 9003 RF, 9003 2nd RF, 9003 Mixer, 9002 OSC, and then three stages of IF at 15 MHz. I can only imagine the noise figure!

Mike WU2D

What is the customary polarization for different modes on 2M and 6M?

Many moons ago, horizontal was the default for 6M AM. Don't know what it is now. On 2M, vertical for FM and horizontal for SSB seems to be the usual. Don't know what folks are doing with AM and/or CW.

73,
ldb
K5WLF

I just got a WRL Globe 6 and 2 hibander.  I need to find a VFO that will work with it. Anyone have any ideas? 

Where do you guys order Xtals? I would like to order some popular freqs for it.  I have a Cushcraft up and cant wait to join the 2 meter AM net.

C

Horizontal polarization is what you need for need for most SSB, AM, and CW contacts on 6 meters. Most FM stations still use vertical polarization. On 2 meters, it depends what you want to do. If you got several local guys all wanting to get on 2 meter AM, and they're not hundred's of miles away, vertical polarization is probably fine. If you want to really reach out, horizontal polarization is the way to go.

Just for clarification, Pete. On 2M is that for some technical reason I haven't heard of, or simply because of common usage?

TNX & 73,
ldb
K5WLF

It always bugged me that 145.8 didn't remain the calling frequency for two meters. I think the band plan designers goofed on that: most 2M AM rigs are rockbound, and changing to the 144.4 range meant having to buy new crystals after many crystal manufacturers have gone out of business.

My 2 cents.

W1AC

used laboratory-grade signal generators might do as VFOs. It is what I often use when fiddling with transmitters. I don't know if they are as stable as necessary but they are of high quality.

Stacked MSquared halos are popular on 2M or whatever name they call them, Big Wheels??

I dont see all that much difference between polarizations, Ive worked stations using a mag mount on their refrigerator 50-60 miles away as well as long wires, open wire fed dipoles and all sorts of other HF antennas used on 6 & 2M. The antennas and location here do give me an edge.

Single or stacked turnstiles will give circular polarization so its a useable compromise that works with either vertical or horizontal at the other end.

Carl
KM1H

One of the hams at work brought in a picture of his dad in the mid 1950's doing a VHF/UHF contest on top of Mt. Monadnock here in NH. He said that his dad pioneered the use of horizontal polarization for VHF DX here in new England and he wrote an article about it.

I think AM has always been horizontal on 2M. I know we used horizontal when I was a kid using my Heath Twoer in a civil defense net. I will ask him more about this tomorrow.

Mike WU2D

Yet many of the 2 meter Gonset Communicator I and II advertising displayed the rig with a 19 inch whip screwed into the SO-239.

(http://www.rigpix.com/gonset/communicator2meter.jpg)

And who was that?

Carl

Hi Carl,

The ham was W1YQI Bill Keyes who lived on Marblehead, Mass. This is from the April 2009 QRZ News:

You may wonder why VHF DXing is almost
exclusively on horizontal polarization.
Horizontal polarization produces a
significant forward scatter enhancement at
the horizon. When I started in Amateur
radio in Connecticut, there was an intense
debate between advocates of horizontal vs.
vertical polarization. I was attending
Northeastern University in Boston at the
time. Connecticut was firmly horizontal
polarization on 2m and Boston was firmly
vertical. Novices were allowed 2m phone
privileges and the NU club station, W1KBN,
had a converted SCR522 which I operated
during many lunch hours.
That is how I met Bill Keyes, W1YQI, in
Marblehead, MA who was advocating a
change to horizontal polarization. The result
was a nightly schedule from Salem, CT to
Marblehead, MA whenever I was at home. I
could always hear his 200w and he usually
heard my 15w. Gradually the tide turned
and horizontal polarization is now the
standard for VHF/UHF DXing.
Well that was a rather long diversion from
the topic of getting ready for the coming 6m
Es season. When the ionization is very
strong signals are huge. An old TV rotator
should easily handle a one to three element
6m beam. M2 and others make horizontal
loop antennas if you don’t want to deal with
a rotator. You may need your old TV
rotator for digital TV after June 12th.
73, George W3FEY

See the attachment on an early NH VHF Contest effort at the end of the newsletter.January VHF Contest circa 1954, W1UIZ/1 Mt. Pack Monadnock, Jaffrey, NH.

Mike WU2D

I dont recognize the name or call but I didnt move to the area until 63.

I did a few stints at Wayne Greens place on Mt Monadnock and also with the W1MHL group on the Pack.

Carl

Mike -  enjoyed the pix of the BC-625.  Brought back memories of the one  I used in my WN2ZPS novice days.  I used a slot car power supply for the 12V DC and a bread boarded HV supply for the 300V.  Ancient WW 1 vintage carbon mic that I got from my granddad.  Worked down to Ft. Monmouth from West Nyack NY one time with it.

I currently have a complete 522 in the case here along with 12V and 24 V dynos that need to be put on  the air sometime.

Where did you get your crystal for 145.45 from?

I had some surplus crystals in the military holders in the low 8 MHz range and wet sanded a couple on 600 paper and stuck them in FT-243 holders. Took about an hour to get 144.400 and 144.450.

Mike

Yes, but that's just one part: the transmitters and receiver might need retuning, the beams would need to be re-matched, and sometimes recut. It's the kind of change that I think we'll look back on years from now and wonder why it happened.

I'm getting old-fogeyitis lately. I guess I'll just have to adapt. Sigh.

73,

Bill W1AC

I checked my logbook and found that I used 145.50 as an AM frequency back then. I had a Benton Harbor Lunchbox and an 8 element beam. We even did a little A4 for a number of months. Using those old rotating drum fax machines with the metal stylii and silver fax paper was so much fun !  :) Breathing in that fax paper smoke was probably a hazard.  :-\

The few years I used xtals I had a couple for the low end, including CW, and a few for working Techs and Novices above 145 that wouldnt bother listening down. It wasnt long before I built a hetrodyne VFO and got rid of that "old junk" ;D

Carl
KM1H

Lots of good info. I think a H beam would work best for my purposes, and also ought to place a discone up there too, maybe on an outrigger.

They are no longer legal, but I was always fascinated by those simple two and three tube XCVRs from some of the Editors and Engineers Handbooks of the late 30's. These circuits used a single triode that doubled as a super-regen receiver or a free running modulated oscillator and the audio section also doubled up as a modulator and RX audio chain. They typically would use a pair of 76's and a 47 or a pair of 6J5's and a 6V6. They worked OK on 5M and up to 2M with these tubes. These modulated oscillator circuits continued tongue-in-cheek through the 40's and 50's but running an oscillator at VHF on the 6 and 2M bands is no longer legal. Here is a late if somewhat complex example of the theme:

http://books.google.com/books?id=390DAAAAMBAJ&pg=RA1-PA231&lpg=RA1-PA231&dq=super+regenerative+6C4&source=bl&ots=VRWVv0vewr&sig=jSZNgsE2qxsRPr7G8sn3PgjrgOU&hl=en&ei=hfGdS-nOFIH98AbE-cy7Cg&sa=X&oi=book_result&ct=result&resnum=7&ved=0CBYQ6AEwBg#v=onepage&q=super%20regenerative%206C4&f=false

A local ham gave me an RME vfh 152.  It hooked it up to the SX28 today for fun. To my total suprise, This thing works FB!  Its output is on 7mhz. I put the 28 on 7, Keyed up the Yaesu 2 meter rig, Tuned the vfo and there I was!  What a neat unit!

It covers 2, 6 and 10.  I got a Globe 6 and 2.  I am going to put shelves in the bud case, then put the RME 45, VHF152 and Globe transmitter all in the case with casters.  I already have a nice 2 meter antenna. But I will add a 6 meter dipole also.

I cant wait to get on the 2 meter AM net!

C

2 meter station now operational!    I got a Globe Hi-bander off fleabay. It needed alot of work. Its now running 25 watts of AM. Sounds great with the D104.  Made one contact so far. Waiting for the net to start on 144.450 AM about 7:30. 

I got the Xtal I needed from AF4k Bryan. Its close enough.. About 1 KC off.  Not bad for an 18 times over Xtal!

C

I was reading the counter wrong..  I am off 10 kc.  Can someone help me?  I need info on raising the Freq of an xtal with a capacitor. I searched around and cant find much info...

Thanks!

Clark

Read up on crystal grinding, its not that hard. You can use a cap for the final kc or so.

Carl

I thnk I might have figured out the issue. The Globe uses a 50PF cap.  The Xtal expects 20. 

C

The 2M station is working nicely but my 20 Watts out of the SCR-522 TX is being heard better than I am hearing everybody else. The little R-508 command set RX is just too noisy. I measured around 1 - 2 uV sensitivity with my old HP608. I can tell that stations are in there but I can not quite copy the outlying stations. When they turn the beam right on me, I hear them.

I am thinking of strapping a preamplifier on the front. I had an old 2M 40673 dual gate mosfet preamp I built many moons ago and simply strapped that in front. Result - very little improvement. The modest noise figure and gain of the mosfet was not enough to set the noise figure of the system and overcome three cascaded pentodes worth of noise!

I could build a better more modern preamplifier with a lower noise figure and more gain. Or I could possibly drop out the two RF amplifier stages and convert them to Fets and run them on the +12V fil voltage.

Ideas?

Mike WU2D

Most flea power 2M rigs are far from 100% modulation, never mind having any enhancements, which makes it hard to copy.

Id opt for FET's in what you have, external additions will overload an already marginal radio. Are you going to have gain control on them?

Carl

I have improved the AGC system in the original radio which consisted of a diode section on the last IF stage and a diode section on the detector first audio tube which is separate from the detector. Never heard of two AGC detectors on separate stages both contributing to the AGC line. One seemed to be for the IF stages and one was primarily to control the two RF stages which are not remote cutoff types. In any case the AGC was weak at best. So I ripped it out and put in a schottky detector and fed the AGC line and re-biased the set point on the RF stages and now it works sweetly. 

Yes the stages will have to be controlled if I go solid state.

Mike WU2D

You'd be far better off dropping a few stages of gain ahead of the first mixer, and let the first stage (your mosfet preamp) set the noise figure for the receiver. None of those early tube VHF RFA stages are worth the powder to blow them to heck these days.  Another important question, what is the IF bandwidth?  If it is excessive that won't help with weaker signal reception either.

Pete k1zjh

Here is the front end showing the 9003 pentodes and the 200V zener regulation I put on the front end stages (mostly for the oscillator) to stabilize it. The IF bandwidth is excellent, around 8 kHz.

I know of few guys who sometimes use 2 merer AM as sort of an intercom, but, for me, 2 meter AM has about as much appeal as warts. I suspect many 2 meter AM rig owners find the rig(s) sitting on a shelf collecting dust. I got rid of most of mine years ago.

During the last secondary peak, I remember checking into two different AM nets on two different openings in the CA area. Also worked England on 6 meter AM during that time.

We have a group of around 10 people here.  Some are on HB rigs, Some on clegg, some on heath. 

I can see one real flaw with 2 meter am.  Lots of the guys use solid state icoms or yaesus.  The receiver is narrow and they complain if you come on of Freq. They have an SSB mentality. 

To me.. You cant be off freq on a boatanchor.. tune me in damn it.

C

With the proliferation of new satellite and digital type activities now appearing more regularity on 2 meters, having a "SSB mentality" is probably not a bad thing. "Wide as a barn door" or having a rig that drifts around the band, probably won't gather you many friends on 2 meters.

We have one Freq that is permitted. 144.450.  The rest of the band is tightly controlled in the valley here. 

C

Just for fun I borrowed an LNA and stuck it in front of the R-508 noisemaker receiver and tried it tonight. It was an LNA-3000 from RF-Bay.

http://cgi.ebay.com/40-3000MHz-5V-Low-Noise-Amplifier-LNA-3000B-New-SMA_W0QQitemZ400079895151QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5d269eba6f#ht_500wt_975

Wow is all I can say. Even with no filter inline, it drastically pepped up the front sensitivity. It has a low enough noise figure and high enough gain to overcome the two pentodes. The AGC works beautifully too and I have not any sign of overload even with aircraft in the 136 MHz range. That is one nice amplifier. Alas it goes back to work tomorrow but I got the message. With a low enough NF and enough gain, all I need is an outboard amp.

Mike WU2D

Be happy that old tube rig isnt bothered by input VSWR.  That looks like an instrumentation amp or something for one of the Icokenseu wide band receivers that all varieties of techs and engineers run around with.

You could build a 2M only version for about a tenth the price if youre serious about pepping up that thing

Carl

It is quite shocking to see what they have been able to do with the wideband MMICs. The gain and noise figures are approaching what some of the best narrowband LNAs of the 1970's could do. The difference is that they are doing it over such a wide band and the match on both input and output is darned good and the IP3 is impressive.

Mike WU2D

What happens if you run Am anywhere you want or SSB or FM for that matter?

In the Albany NY area, perhaps we don't have as many repeaters but I think so long as your not operating on an input or output frequency, there shouldn't be a problem? Am I wrong? Just now getting back into 2 Meter AM.

ITs a gentlemans agreement. As long as your not bothering a repeater your prob fine.

C

AM runs below the FM stuff, no one will hear you up in that area but it could be fine for semi private QSO's on dead frequencies.  The problem is the dweebs running the APRS and other pointy head stuff ;D down around 144.4. They think they own wherever they plop. There should be plenty of room in the 144.4 to 144.6 area, just listen around during peak hours.

Carl
KM1H

Not hear.. 2 meter is a very active band.

C

 :) Yes, I agree too. 50.400 is a great place to to do AM !