My first contact

[AB1GX]

I tried for a few hours to break into 3.885 mHz to meet some AM folks on the air (according to the band plan), BUT that meet slot seems to be the permanent domain of a bunch of big mouth 1.5 KW AMer's.  It looks like I'll need to finish my class e rig and a much better antenna to play.

So, I turned on two boat anchors and talked to myself for a while....

[WA1GFZ]

remember the rule of PW and you don't need an IQ test to operate am

[Todd, KA1KAQ]

I tried for a few hours to break into 3885 mHz to meet some AM folks on the air (according to the band plan), BUT that meet slot seems to be the permanent domain of a bunch of big mouth 1.5 KW AMer's.  It looks like I'll need to finish my class e rig and a much better antenna to play.

Now, now....no need to get your undies in a bunch here.

Rule #1: It's AM, it's fun, it's only annoying if you make it so by getting too upset, taking things too seriously, etc.

Rule #2: Don't restrict yourself to a dysfunctional band plan. AMers are the only ones who ever respected it. Even the Amateur Radio Retail Lobby only mentions 3.885 as a calling frequency. With the band expansion for phone down to 3600, there's plenty of space and plenty more AM activity below 3800. I was on with a group until 8:30 or so last night on 3723. WA1HLR, W1RC, VE3AJM and others were around after the 'After Dinner' gathering on 3733. Later while making dinner I heard Steve, W8TOW operating cross mode on 3715 with a SSB station.

Rule #3: Never bring a knife to a gunfight, unless you're carrying a big gun too. Especially if you hope to operate in the 75m cesspool during prime time. Some nights it's quiet up there, but seldom. Most nights resemble hand-to-hand combat if you're not running some power along with the stations you're communicating with. Sorry, that's just the way it is up there and has been - for years. Decades, even.

Rather than starting out by confining your activities, move around regularly and get a feel for what's out there. There's no guarantee you'll like every AMer, every group, every style. When all else fails, find a clear frequency and call CQ. Even if you wait to do this until you get your feet wet, it's still the best way to create activity.

With all of the folks operating, discovering, and returning to AM, there's no reason whatsoever to be confined to one QSO on one frequency with one large group. Especially with the available space available. If AMers don't use it, you can bet SSBers will, with the ensuing ownership issues.

[W1DAN]

Hi:

I have had this experience as well. Frustrating.

The daytime is better for low power AM as you are not fighting QRM, and there are other AM'ers that do not mind talking to non-tall signals. I have also found that some AM'ers are fast at the transmit trigger or bay have their RF gain turned down.

Try again until you find someone willing to chat with the smaller signals.

When 10M eventiually opens, a low power signal will go far and it'll be lotsa fun.

You are welcome here. Feel free to ask questions.

73,
Dan
W1DAN

[Steve - WB3HUZ]

Tom:

Don't give up. You didn't say what you were running (power and antenna). It can be tough in the evenings sometimes with crowded band conditions and lots of QRM.

I remember the first time I tried to get into a QSO running just 40 watts and an end-fed 60 foot piece of wire up about 30 feet. It was tough and only a few guys could actually copy. I got a few signal reports like, "you're 40 dB UNDER S-9!"That's the way it goes sometimes. Don't take it personally.

I just used the experience as motivation to put up a better antenna and get a TX going with higher power.

I'll be listening for you. 73.

[flintstone mop]

Don't give up!!!
Some folks will disagree with me BUT 200 watts min. and a real antenna (BIG long dipole fed with open feeders, BIG HB tuner Or a resonant 50 ohm antenna) for whatever band you want to work. At least 50 feet in the air.
Many folks get frustrated with 25 watts and a compromise antenna. 40M daytime is really nice for the low power folks 7290+ or -.
Fred

[AB1GX]

Everyone, thanks for the helpful info!!!

I just checked my AM power and it's about 200W, but my antenna is the problem (based on your comments).

The main issue appears to be antenna height.  Fifty feet is a long way up for a dipole on the 75-meter band.  I'll cut a dipole to resonance and put it up 20 feet or so.  At that height it will probably be 20 Ohms or less.  I guess a transformer feed is the way to go.  Maybe a reflective parasitic element might be in order to keep the energy going is a useful direction...

Tom, AB1GX

[WA3VJB]

of a bunch of big mouth 1.5 KW AMer's.

Tom did you intend to make a first impression just yet ?

[AB1GX]

of a bunch of big mouth 1.5 KW AMer's.

Tom did you intend to make a first impression just yet ?

Yeah, I want to be one those AM big mouths.  But my power amp just isn't big enough.

[WA3VJB]

I see.

[k4kyv]

Fifty feet is a long way up for a dipole on the 75-meter band.  I'll cut a dipole to resonance and put it up 20 feet or so.  At that height it will probably be 20 Ohms or less.  I guess a transformer feed is the way to go.  Maybe a reflective parasitic element might be in order to keep the energy going is a useful direction...

Can't you get it up another 10 ft to get the total elevation to about 30 ft?  From my experience, 30 ft is about the minimum for good performance on 75/80.  That last few feet makes a big difference.  The best way to feed it if you want to work the entire frequency range of the band is to use open wire tuned feeders and a tuner (not one of those bogus things so popular today, with an unbalanced T-network feeding a balun inserted between the tuner and the feedline).   

The balun needs to go between the transmitter and the tuner, and if the tuner isn't inherently balanced with split stator capacitors, etc., isolate it from ground by setting it on insulating material such as ceramic standoffs, pieces of wood, or even a couple of good thick books.  With this configuration, it is perfectly normal for the case of the tuner to be hot with rf.  Just be careful when adjusting the settings, so that you touch the knob, but not the case.

You could feed the dipole directly with coax, but you probably won't be able to work the entire band.  But don't get hung up on SWR.  It doesn't have to be exactly 1.0:1.  Anything below 2.5:1 will work just fine, if you can get the transmitter to load into it.  My vertical on 160 shows 3:1 at the extreme ends of the band, and I don't notice any drop off in performance.  Of course, if you are running a modern solid state transceiver, high SWR may cause the rig to run at reduced power or shut down entirely.  A low dipole may not exhibit anything near 1:1 SWR, even at its resonant frequency.

In that case, the  solution is a "transmatch."  The difference between a transmatch and an antenna tuner is that the antenna tuner is designed to match a wide variety of balanced or unbalanced feedline impedances. This includes open wire tuned feeders, random length wires, etc.  A transmatch, on the other hand, is an unbalanced tuning network designed to transform the load presented at the transmitter end of a coax feeder, which may vary considerably due to mismatch between the coax and the antenna, to 50 ohms nonreactive, so that a transmitter with limited a range of load impedance it will load into, will operate into that antenna at full power.  In other words, the transmatch compensates for SWR on the coax feedline.

At 20-30 ft. off the ground, I doubt that a parasitic element would be effective on 75m.  It would be much less work to simply get the dipole up higher, than to try to add a director and/or reflector, and the higher elevation of the simple dipole would work much better, and be omnidirectional.  At low elevations, less than a quarter wavelength in height, a simple dipole is just as omnidirectional as a vertical.  The null off the ends shows up only at antenna heights approaching a half wavelength and at longer distances.  On 80/75, that would be 100 ft. high or more, and 2000 miles away and beyond.

[steve_qix]

Hmmmmmm..  When did this happen and who was in the QSO ?    I know for myself, and the folks I was talking with tonight, if someone breaks in and we can hear anything at all, we'll pause for the "breaker" and let him into the QSO.

But, I will say this, nighttime is tough unless you are pretty strapping.  The slop-bucket interference is high, and tonight (and throughout the summer) the static will be a major factor.

There are stations that do pretty well during the day who will literally disappear at night - we will barely be able to tell they're there.

Antenna height is REALLY REALLY important, and at night in particular.  The so-called "strappers" all have high antennas.  50 feet is good - 80 is very good, but at least 50 is starting to approach a quarter wave in  height.

When I first got on 75 meters, I was a "piss-weaker" until I got my antenna up over 50 feet.  The transformation was AMAZING - I remember it still (and this was 35 years ago!).  Like Rodney Dangerfield - I "didn't get no respect" until I got that antenna up in the tops of the trees   

Regards,

Steve

[AB1GX]

I guess size matters, BUT a dipole 80 feet up in the air

How about a 1/4 wave vertical?  I don't mind putting some copper in the ground (and zap some moles).  Will I still be able to bend your S-meter?

[Steve - WB3HUZ]

Go with the dipole bro. A vertical is great for talking to stations 1000 miles or more out. A dipole is what ya need for the local rap. Give it another try. May just have been a bad night.

[w3jn]

I have a dipole up 30-35' or so and it works FB.  Feed it with a K1JJ design homebrew tuner and W7FG ladder line and you'll have no problem.

The dipole/W7FG feedline was the cheapest and BEST investment I ever made in my station.

Don't give it up.  But I suggest you look around towards the lower end of the band where the QRM isn't so bad.  There's a group on 3733 that meets every afternoon about 5 PM that might be a better bet than trying battle the typical slopbucket nets that encroach at 3880-3885 every night.

[AB1GX]

I have a dipole up 30-35' or so and it works FB.  Feed it with a K1JJ design homebrew tuner and W7FG ladder line and you'll have no problem.

Okay.  So if I understand, you're saying feed the dipole with a 600 Ohm ladder line.  But doesn't that mean that the antenna needs to be a folded dipole (to get the impedance up)?  The loss on ladder line is virtually zero, but at 3.9 mHz the insertion loss for 150' of coax is also extremely low.  And ladder line means HIGH VOLTAGE...

The K1JJ tuner makes sense.  It matches the 50 Ohm transmitter/coax to the 600 Ohm ladder line (and tunes the antenna).  BUT - Wouldn't it be better to put the tuner up at the dipole feed point and use coax all the way?  So the antenna doesn't de-tune when it gets windy.

I guess I don't really understand why one would put the tuner near the transmitter rather than at the antenna.  Perhaps the tuner driving a 600 ladder line is the tradeoff.  Easy location to tune and reasonable insertion loss from the indoor tuner to dipole feed point.

[Steve - WB3HUZ]

If you only want to use your dipole on one band (i.e. 80/75 meters) go with the coax. It's simpler and no tuner is needed (probably, depends on how sensitive your transmitter is to SWR). But if you want to use it on many bands, your are better off going with the open-wire line and a tuner.

You are correct that the insertion loss of coax at 3.9 MHz is low. But it will go up very quickly as the SWR rises. Try running some numbers at the link below.

http://fermi.la.asu.edu/w9cf/tran/index.html

You are correct in thinking that from an absolute performance standpoint you'd want to put the tuner right at the feedpoint. The drawback is that you now have a big, heavy tuner hanging off your antenna. And you'll need to remotely control it. So, the tradeoff is made to put the tuner in the shack, within easy reach of the station op. The tradeoff is a good one because the loss in good open wire line is nearly zero throughout the HF spectrum. Even at high SWR, the loss is very low. Once again, run some number on open-wire line with the transmission line applet.

Using open-wire line does not necessarily mean high voltage. As with any feedline, coax or open-wire, the voltage and current varies along the length of the line based on the frequency and the SWR. Even if the voltage does get high, the breakdown of even one-inch spaced open wire line is ten of thousand of volts.

As far as the antenna detune when the wind blow, I've never seen this happen. Yes, in some situations (depends largely on the Q of the system) you will see slight changes in tuning as the antenna and/or feedline moves around. These were never enough to cause any problems with my operation.

As you well know, all this stuff involves various parameters and tradeoffs. Finding the mix that works and will fit your needs and operating requirements is the fun part.

I have a dipole up 30-35' or so and it works FB.  Feed it with a K1JJ design homebrew tuner and W7FG ladder line and you'll have no problem.

Okay.  So if I understand, you're saying feed the dipole with a 600 Ohm ladder line.  But doesn't that mean that the antenna needs to be a folded dipole (to get the impedance up)?  The loss on ladder line is virtually zero, but at 3.9 mHz the insertion loss for 150' of coax is also extremely low.  And ladder line means HIGH VOLTAGE...

The K1JJ tuner makes sense.  It matches the 50 Ohm transmitter/coax to the 600 Ohm ladder line (and tunes the antenna).  BUT - Wouldn't it be better to put the tuner up at the dipole feed point and use coax all the way?  So the antenna doesn't de-tune when it gets windy.

I guess I don't really understand why one would put the tuner near the transmitter rather than at the antenna.  Perhaps the tuner driving a 600 ladder line is the tradeoff.  Easy location to tune and reasonable insertion loss from the indoor tuner to dipole feed point.

[The Slab Bacon]

Use ladda line and a good strapping tuna, you will never regret it! I have had very good luck with short, non resonant antennas feeding them with ladda line. The losses are minimal, you can adjust the tuna to go just about anywhere, and you can get by with having only 1 antenna.

However the installation of ladda line is a bit more tricky. You have to be careful to keep it away from metallic objects and other considerations also come into play. Coass is an easier install, but ladda line is a better job. You have to figger out which one works for you. (I'll never go back to a coass fed antenna!)(at least not a wire dipole or inverted V)
                                      The Slab Bacon

[AB1GX]

Thanks Steve.

Yes, the antenna will be for 75 meter AM transmit only.  I currently use an S-38A (5-tube AC/DC) with a 15' antenna in my basement for 75 meter AM reception and it works great!  With the AM power being used, I could get away with a crystal set.

I'm thinking about adding the antenna tuner right into a class e transmitter that I'm building and drive the antenna with a single box in the sky.  Instead of a feed line, I'd need to only a run a pair of 10 gauge wires to supply power (from modulator) and a TTL twisted pair for a squareware.  I might use two pairs of nylon ropes from the feed point to turn levers for final/antenna tune.  My field strength meter will finally come in handy.

This AM stuff is much harder than I originally thought it would be, especially when you're limited to only 1.5 KW!

[kc2ifr]

Bacon,
U hit the nail right on the head.......coass is for sissies and sidebanders.....

[AB1GX]

Slab, got it. That's the best approach for multi-band operation.

BUT... I haven't heard any AM on any other HF bands.

[Steve - WB3HUZ]

LOL. Those two 10 gauge wire would make for some nice open-wire line.

AM on other bands

160: around 1885, 1945 and 1985 kHz
40: 7290/95 mostly daylight hours
20: 14286 approx 7-8PM ET

Not much on the higher freq bands these days with the low sunspot number, but in a few years those bands will be hopping with AM, especially 10 meters from 29.0 to 29.2 MHz

[AB1GX]

LOL. Those two 10 gauge wire would make for some nice open-wire line.

It's a good thing that I have ferrite cores left from my class e project.  I can make plenty of chokes for power supply lines.

20 meters sounds interesting!

[flintstone mop]

Yea Tom,
20M is a real nice band for AM but you will be in QSO with Hams much further away and at the most two or three of you will have a nice QSO. 20M gets quirky with skip and distance. Not a good "local" (100-300 or more miles) band.  40M and 80M are pefect for the big roundtables. 160M is very exciting and more of an antenna challenge than 80 and 40. The antennas described so far for 80 and 40 are fairly easy to get up and running..........and YES 50 feet is a good starting point. A sling shot and some nice trees makes a nice aerial holder. Can you decribe your QTH? Lottsa trees/pines ?
Fred

[AB1GX]

Fred,

My backyard slopes down to east for 250 feet.  I have many 50+ foot trees, oaks I believe.

So if I understand you, it's okay to drape the antenna on the tops of trees and a KW or so won't set them on fire or cook the critters in the trees.

To me, 80 meters is a hobby, 160 meters is a career.  Anyway, I haven't heard squat in the way of AM on 160 meters.

Tom
AB1GX