The AM Forum

i just passed my general today. I have a some questions about operating on 75/80m am mode. If anyone can help me out please either direct me to a link or if you can pm me your number maybe i can call someone and talk to them.

thanks
brandon.
kf5iia

Hey Brandon, welcome !

What kind of information do you need?

1. Equipment selection / acquisition

2. Using your existing HF gear on AM

3. Where to find AM activity

Congratulations, welcome aboard!

73, Bill

the main thing would be how far should you move from a qso to start another.

and where should you keep the a.m. to without offending people.

thanks bill. i have been listening for a little over a year. and really enjoy it.

heh heh

I just PM'd you.

What seems to be the most likely to irritate people, if anything, is when someone joins a conversation with NO clue what's being talked about.

It's kind of like merging on the highway: Best approach is to come up to speed, notice what's going on around you, and people will let you kn.

That's about it.

Congrats on the General Class license.

Looking forward to hearing you.

i do understand. mess the whole flow of things up quick.

Brandon, if you haven't already, I most strongly urge you to buy the following books:

ARRL Handbook:  immediately! good overall information that can answer many of your starting questions incl. general procedures, theory, basic antenna setups, construction projects.
ARRL Operating Manual:  Goes more in depth on procedures, Dx'ing, QSL's etc.
ARRL Antenna Manual:  Broad coverage of antenna theory and construction.  For when you want to get deeper into antenna experimentation.

You can buy them new, or easily find used ones.  Even copies ten or twenty years old are useful since the basic info doesn't really change.  You will find these books useful for reference for years.

Bill   

See the article at the link below.

http://www.amwindow.org/tech/htm/ambw.html


As to your second question, see the link below but any clear frequency is fair game.

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

Thanks for the replys...

I think i am good to go now for a little while.

Brandon,

Great on passing your General.  Even better, you're interested in operating on AM.

Best way to learn how to operate is to get on the air.  Get on around 3885KHz and break into any AM QSO you hear.  Just drop your call in between transmissions and the guys will pick you up.   You may have to try a few times before being heard.

After a few QSO's you'll be an expert operator like me ;D

Don't worry about making any mistakes,  even long-time operators make them (except me, I never make any, regardless of what some of the AM'ers may say about me)

Not sure what equipment you have, but you will need an AM transmitter and an antenna that will work on 75M.  Just let us know if you need help with knowing how to get an antenna up.  You can make a simple dipole antenna from most any kind of wire and some coax cable.

Fred,  KA2DZT

I am going to mess with my dipole this morning. i have the center up about 55 feet. The ends taper down to 8 foot high.

Yea on getting the antenna up. i alsmot threw my arm out with a socket and some string. i finally got the fishing pole out and the rest was easy.

Brandon,

Congratulations on passing your general!

You have gotten some great advice so far and the only thing I can add is that you will make a few mistakes because everyone does.  So don't sweat the little stuff!  With your QTH you will sweat enough given the climate  ;)  I grew up in Gulfport MS and I know heat and humidity.

My first key mistake was made during my first day on the air as a new novice in 1975.  My new to me Johnson Valiant came with a couple of crystals and I used those crystals along with the procedure in the manual and my  Hallicrafters SX-62 receiver to calibrate the transmitter VFO.  I carefully set the VFO near the middle of the old novice segment on 40 and called CQ for the first time and I got a response!  Unfortunately it was, "WN5NSC you are out of the novice band".  Those two beautiful FT-243 rocks that came with the Valiant had been moved in frequency by the previous owner but the markings had not been changed.  I was one scared 14 year old for the next week waiting for the feds to come knocking on the door.

Suffice to say I survived that mistake and a few more over the years.  Welcome to AM.

Rodger WQ9E

Will that fit on a neon sign?

Don't worry about offending anyone. If you operate A.M. you're already offensive. It comes with the territory!

As HUZman said, any clear frequency is fair game.

55 ft high at the center is a good height,  higher than what a lot of hams have.  You should have no problem getting out.

I've done the same with my arm trying to throw lines over tree tops.  I've been using a fishing pole for years to get lines up.  Tie a orange or other bright color ribbon to the sinker,  it makes it a lot easier to find the weight when it comes down.

Fred,  KA2DZT

Congrats Brandon! Just jump on any QSO on 3.885 mHz and the guys will be happy to welcome you. Just understand that night time can be a bit difficult and requires some signal. A good time to get your feet wet is early afternoon before the band goes long. There are many AM'ers out there running everything from restored broadcast, riceboxs too class-E rigs.
You will have a great time! WELCOME ABOARD!

Brent W1IA
Derry, NH

Congrats, Brandon!! Welcome to the wild and woolly world of AM!!

Just dont be like Fred and break "the first rule of the piss-weaker"
(the weaker they are, the longer they talk) Or like we do to Fred "Bang, lookie here, squashed just like a bug"  ;D  ;D

Get out there and STRAP! ! ! ! ! ! ! ! !

I am sure going to try. i worked on my dipole all day. it tuned in nice. 

only problem i am having....

i am going from valiant threw a metal box withe the scope pickup. i forgot who posted the info on it but where the wire from the coax goes straight threw and you put your pickup wire next to it.

from there i go to an antenna switch.

when i transmit into dumy load all is well on the scope.

when transmitting over the air threw the dipole my pattern on scope is distorted.  i still get two bars of carrier but the postitive peaks on top act normal but the positive peaks going down look cut off. i can still see that my carrier is not pinching off but it just bothers me having this one little bug.

audio report on air is it sound fine. i know it is just a problem with the scope/pickup

anyone have this problem before?

That's cause the antenna and the dummy load have different reactive componants.
A little retuning into the antenna with an eye on the scope will help.

the other reason may be rf pickup by the scope thru an undesired path.

Good job Brandon. On or off the air, AM means fun and manly electronic equipment.

The answer to one of your original questions depends a little on your signal strength and the signal strength of nearby stations. BUT assuming that things are Q5 on all sides, then 7kHz is about the minimum distance between carrier frequencies that is good, sometime 5kHz happens, and 10kHz is more betterer, beyond that, unless you have HF splatter or artifacts (no one EVER has them!) you are essentially "invisible".

But as a new station, if you can easily break into existing QSOs then you've got enough signal strength and a good ant... so after that calling CQ on a "dead band" or open frequency would make sense... also try to start out at times when propagation is good, but the freqs are not too crowded with "tall ships". Nothing much is worse or more frustrating for the operator than when a weak station trying to break into a busy QSO dominated by stations with real power and good antennas. But even then, if its not Saturday night, up here in the Northeast plenty of mobiles and newbies get in all the time...

Congrats on your license! Enjoy!

            :D

                          _-_-bear


PS. be cautious about what these folks here tell you, they can be misleading. For example, you do not need to buff antenna wax at all. You did put it on your dipole??

no, i'm have to look on ebay for some. hahahah

Brandon congratulations and welcome; I'll be looking for you on 75 or 160 this fall/winter.  I am still trying to figure this stuff out myself so welcome to the club  Your question about the flat tops got me studying again.  :D

Rob

well i made my first contact. w5dud

then the valiant had a small fire.

there are two pairs of mica caps seriesed to ground off the back of the band switch. well one pair didnt make it.

i'm goan to see if i can figure out how to post a picture.

(http://img838.imageshack.us/img838/3527/smokeo.jpg)

got them changed.

gona try again tomm.

Hey Brandon,

Welcome to the best of ham radio!  You being in Pearl River and me south of Lafayette means we are at a great distance for awesome daytime 80 meter AM. 


Talk to you on the air,

73, John KX5JT

yep, i have heard you on a 3 foot piece of wire. hahahaha

Great on hearing John on the three footer,  just don't try to transmit back to him with it.  Your Valiant may experience another small fire followed by a minor explosion ;D

Fred,  KA2DZT

Brandon,

Those replacement small mica caps are not going to stand up to typical AM transmissions, you might get away with them on CW if you keep the dashes very short :)  The original mica "turnstyle" cap had considerably more RF current capacity than these small receiving type replacements.  Unfortunately the turnstyle originals were very prone to failure like the one that was in your transmitter.

You are going to need some small transmitting type mica caps.  I imagine you also noted some changes in loading during transmission as these caps heat up and change capacity.

yes i did. i noticed my carrier got very small on scope. and my plate current was pegged. so i unkeyed.

after his transmission they must have cooled. i keyed back up. they lasted about 45 seconds or so and up in smoke.

only thing i have in the correct capacitance range is a big door knob cap i am going to put in there.

i am cutting some 8-32's down short enough now to bolt it in.

Hi Brandon,

    Congratulations on choosing AM.

Your padder capacitors must be able to handle some R.F. current where they are located. Replacing the existing cooked ones with the same thing will yield the same result.

Whatcha gotta do is come up with the same capacitance value but a higher current rating. The solution depends on what parts you have on hand or can source.

If the caps are 1000pf the simple way would be to parallel smaller capicitance units and share the current. 10 X 100 pf or 5 X 200 pf would probably hang in there.

Obviously a series/parallel deal might work also.

There are a lot of prople here who know your tx inside and out.

Dave W2VW.

well i am back on the air untill i find another weak part of my station.  ;D

Brandon,

If you cannot find some suitable vintage doorknob or large mica caps, take a look at the CDE MCM series RF chip caps.  They are SMD but you can add leads easily.  The price is not terrible and they have a decent RF current capability.  Mouser and Digikey are both stocking suppliers. 

I replaced the string of caps off the back of the band switch with a large doorknob. i think it will be ok.

i still have somethign heating up, after transmitting for a minute or so i have to re dip the plate.

i dont know if i should re investigate or just wait for the smoke signal of trouble again. hahaha

Hi Brandon,

Sounds like you know what you're doing there.  You'll get that station working FB in due time.

Try this technique to find the components that are heating up:  Take the rig outa the cabinet and load it up. Wait for the plate current (or whatever is changing) to occur, then spray suspected components with that cold spray stuff you can find at Radio Shark.  When you hit the right part the current will swing back to normal.

This does not apply to VFO/frequency sensitive components, as they will be affected big time even when good.

As an alternative, use a hair dryer and blow heat on the suspected areas to see the symptoms. Then the cold spray is your rifle shot to zero in. Be careful not to melt anything or overheat with the hair dryer. Alternating back and forth can kick bad components out on their asses fast.

T

...also, if ya use the spray, be carefull Not to let the cooling spray go UP the tube sockets..... the tubes do not like this and they will say so quickely. Ask me how I know.....


klc

thanks for the comments and help.

it did this one antenna nad dummy load.

also when i loaded up on the high bands where the aux is bypassed it did not do it.

i isolated the aux coupling and got pf readings on each setting.

for right now i seriesed two .005 1200v old mica's big block ones.

because that is within 150pf of where it was at. i think i will be able to get the rest with the air variable.

this valiant used a small cap with 4 lugs on it. another valiant i have uses 4 individual old mica's

so i really think this was the weak link and i am going to try to gather parts to get the aux switch back 100 percnet with better componets.

thanks again for the warm welcome..
brandon kf5iia

I have some mica tx caps; maybe I can send you some--they are the brown sangamo jobs that are about an inch long, half inch thick, and 3/4 inch wide.  let me know the cap value, and voltage, but I don't know much at all about the Valiant so I don't know for sure if these are what belong in there.

Be extremely careful inside an operating Valiant.  There is exposed HV at many points with plenty of current available and it is an "accident rich" environment.  Say for example, you accidentally spray and shatter a tube as noted by the previous poster.  You will probably jerk your hand back in surprise and hopefully not come in contact with a voltage source.  Many years ago I read a GE publication where they detailed accidents involving TV/radio repairmen and one of the more common accidents involved servicemen hurt by an imploding picture tube after they received a fairly minor shock and hit the fragile neck of the tube while jerking back from the shock.

I would first visually check for capacitors in the RF path not suitable for RF, if small dipped micas like those in your photo are present in the loading circuit they are simply not going to handle the RF current from the Valiant.  This includes the coupling cap C37 which should be at least 1000 pf for operation on 80 and preferably larger.  The later Valiants and Valiant II were built with a 2,000 pf cap which is suitable for proper operation on 80 and 160.  If the proper caps are in place, run the Valiant into a dummy load to make sure that the issue is not in your antenna system.  If the grid drive drops, this is likely from the coupling caps to the final grid which fail fairly often.  Try the Valiant on a higher band (10 or 15) at which point you should typically have the auxiliary coupling caps out of the circuit when fully loaded.  Visually inspect both the band switch and coarse loading switch contacts for heat damage and also the solder connection to the RF out SO-239.

 

the grid current stays the same.

also acts same on dummyload or dipole.

i did notice the contact was black on the aux coupling.

i am going to take it back down tomm. and i guess bypass the aux switch and see if that helps.

i may also try to get some of that spray.

Brandon.  Next time you are inside the valiant.  Take a tooth brush and some contact cleaner such as deoxit and clean the band and loading switches. Turn the switch and scrub the contacts and wafer clean.  If you look close, There are small rivits and you will likely seen carbon traces from the rivits to the contacts.  These arc and then blow out the caps or worse, Torches the switch.  Very common problem and an easy solution.

C

Nice working you right now on 3890 AM Brandon!  The Valiant with the 811A's modulating sounds great!  You're doing great!

John KX5JT

I can barely hear you guys.   Not enough to talk, to much noise.. But I heard your voice JT.

C

Hey Clark cool!  WW9W came in after (now on with him about to sign)... he's on his BC610 near Dallas.

Hey Brandon and anyone else....

Don't forget the AMI west coast net that you can listen and watch on

http://stickam.com/wj6w

:)  Around 2:30 utc people start gathering.. Net starts officially at 03:00 utc

(that's 8pm Pacific, 10pm Central and 11pm Eastern ... DOES it run on Collins night?)

yes in deed very cool... I'm having a great time. Good talking with you john. you were putting a great quality signal over here. i'm about to go back in the shack and listen some more.

JT,

  ...  "DOES it run on Collins night?) "

YES,  EVERY  Wednesday night.

Brandon,  Welcome here and to AM.  Congratulations.  Have Fun,  Vic

Thanks i am having a great time...