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Is 200w enough for 75 AM in the midwest?

Discussion in 'Amplitude Modulation' started by K8CCA, Mar 13, 2019.

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  1. K8CCA

    K8CCA Ham Member QRZ Page

    How much power is really needed for AM? Is 200W enough? I have been trying to get a vintage AM station on the air for the last couple winters. Last winter, I worked on a Johnson Viking 2 for a while until I figured out the mod transformer was bad, and I could never find any proper crystals. So I got sick of it and sold it at Dayton. Then in the summer, I picked up a couple Valiants, and a couple Rangers. I have worked on the Valiants this winter, only to find that one has a missing LV transformer and the other has a bad HV transformer. I guess I need to transplant transformers from one to the other or find a couple transformers. Then in the last week, I have been working on recapping a Ranger and the Courier Amp, which I am almost done with. So last night I was listening to a group on 75meters and tried to jump in with my Icom 7300, but I don’t think anyone could hear me, looked like it was about 30w. Was my first time trying AM. Maybe this weekend, I will have the Ranger done, and with the Courier Amp, I should be around 200w AM, so hopefully that all goes well.
     
  2. AA5CT

    AA5CT Ham Member QRZ Page

    Carrier or amplifier "peak" output?

    200W carrier works fine from an SB-220 ... thats 800 W pk ...

    You antenna also plays a part, what are you using for an antenna?
     
  3. WA5VGO

    WA5VGO Ham Member QRZ Page

    Properly tuned, a Johnson Courier will only deliver around 60-70 watts carrier on AM. Adding it to a Ranger isn’t worthwhile.

    The Valiant is a more worthwhile endeavor. You can get close to 150 watts carrier. That won’t make you the channel master, but it will deliver a decent signal.

    Darrell
     
    K9ASE and KM1H like this.
  4. K4KYV

    K4KYV Subscriber QRZ Page

    200w, 100% modulated with decent audio, can be expected to make a great improvement over 30w. A good antenna helps as well.

    With the two Valiants, you should have enough parts on hand to get one good one on the air, unless both happen to need a major component like a plate or modulation transformer. I'd put the one that's in best shape on the air, and use the other as a parts source. You could probably trade or peddle the extra cabinet if it's in good aesthetic condition on-line or on ePay. The remainder of the carcass could be put aside for parts, or if that takes up too much space, carefully strip it and save the components. The extra VFO (or its components if the whole thing doesn't come out as a module) would be worth saving, as well as all the specialised mechanical stuff.

    The same goes for the two Rangers. I'd get one going first, using the other for parts if necessary, and then the other one if there is enough left to be restorable. If not, use the other one for parts.

    You can never have too many spare components on hand for a rig you are using. Rangers and Valiants are not vintage items too rare to part one out to get another one working.

    75m is populated sparsely enough these days to allow one to get out with 100-200 watts at night. The greatest obstacle in the coming months will be the spring/summer QRN.
     
    N2EY, WA3VJB and AC0OB like this.
  5. WA3VJB

    WA3VJB Ham Member QRZ Page

    Nice to see your efforts at putting together a station among various transmitters you've got.

    Among contemporary rigs, the typical SDR with an amplifier runs a couple hundred watts on AM; so does the "Super Senior" AM transmiter. Both do well under most conditions on 75 meters, except perhaps when the band has gone long and signals decline. From your location at Michigan you should easily keep company with the healthy midwest AM community, and you could test your system farther out with some of the regular gatherings on 3885 where there are check-ins and an anchor station.

    For years I have used 250 Watts on 75m at night and have been heard coast-to-coast, north-and-south of my location near Annapolis. I enjoyed a vast improvement elevating my simple dipole from 40-50 feet to about 90 feet with fresh coax. On receive, I can hear most stations in the 100 watt "desktop" category (Valiants, DX100, 32V, etc.). And even when the band is long, I credit good reports despite weaker signals to my running a high modulation index.

    So, good luck, and I think you'll get some good results if your antenna system is adequate.
     
    Last edited: Mar 13, 2019
  6. N2DTS

    N2DTS Ham Member QRZ Page

    Should be with a half decent antenna.
    25 watts out of the icom 7300 should also work for some qso's at some points of the day depending on how far the skip is.
    I did 1000 miles on 40 meters at night with 4 watts and local 80 meter stuff at 2 watts.
    People heard me quite well they said.
    If you run low power, its best to make long transmissions, the guys will love that! Tradition must be observed.

    100 watts and a full size dipole up 35 feet should be good for loads of solid qso's with good band conditions.
    80 meters often dies at 630 or 7 pm then comes back or is long after 9 pm or so lately.

    You might not get a great response if you try and break into a big group with a small signal.
    Call cq, you never know how many guys are listening or where the band is open to.
    7290 and there abouts is often good at night for longer skip, and late morning for more local work (weekends) and the noon time forum is on at noon every day I think.

    You should be able to work the east coast and west coast guys from the center of the country.
     
  7. K8CCA

    K8CCA Ham Member QRZ Page

    Cool, thanks for the heads up. I thought the Courier would put out 200w. I just looked back in the manual and see that it's 200w input. Duh!

    Yeah, I was trying to get both the Valiants working. I worked on the one that was completed, but had tons of mods, even had a 4th 6146 in the PA, so it was a bear getting back going. I was really disappointed after I worked thru it all, and then found that the HV xfmr was shorted. I am going to Dayton, so maybe I can find a transformer there. Although Heyboer Transformers is only 30 miles away, and they can make a new LV transformer for $130, so that's probably a better way to go anyway.

    On Antennas, I have a Caroline Windom up at about 50' for 40 and 80 and 4 el Mosely on 10-15-20.

    I do have a Drake L4B hooked to my IC-7300, but I was unsure how much AM it could safely run. Maybe I should try and figure that out and get on AM with that setup, since spring is right around the corner.
     
  8. K5UJ

    K5UJ Ham Member QRZ Page

    Is N watts enough? This is a frequently asked question; most of us probably wondered about this at some point. Answers are typically all over the place but in my opinion, you almost can't run too much power on ham AM. Oh sure, if you were to somehow run 50KW it would be too much in a lot of ways but let's get back to real limits and possibilities. Assuming you have a common antenna among AMers like a dipole fed with ladder line at 50 feet and full clear audio, more power is always better. But you asked, is 200 w. enough? It depends on what level of enjoyment you want, and how often you want to put out an enjoyable signal. Enjoyment in AM is usually defined as comfortable easy ragchew QSOs, where you're getting a nice strong speaker quality signal and you can kick back and relax, as if you're sitting around with some buddies gathered in front of a nice fire in your fireplace. The opposite of that is wearing cans and straining to understand slightly distorted audio wafting above and below the noise level while the op at the other end talks for 10 minutes about his new CW decoding box. In between that are probably 60 or 70% of QSOs, because many ops have stations that are usually okay and readable, but not the full strapping shack filling audio that makes us all sit back and think what a kick ass hobby this is. What percentage of your QSOs are enjoyable for you and the guy you are working? You need to put out an enjoyable signal as well as receive one. Some nights are great; others not so much. More power increases your odds of having more good experiences. Besides propagation condx; other variables are the receiving operators' environments. Maybe some are in high noise level locations. Nowadays more power is needed to overcome that. Some guys are content with 100 watts. They're okay with a few good nights and walking away to do something else otherwise. You'll just have to operate and decide if what you have is satisfying. I'm usually not satisfied with what I can hear and deliver. I want the operators I work to enjoy my signal as much as possible.

    Unless you're in love with the Courier, I'd unload it to some collector. It's not worth messing around with in my opinion.
     
    Last edited: Mar 14, 2019
  9. N2DTS

    N2DTS Ham Member QRZ Page

    It goes something like this, IF THE POWER SUPPLY CAN HANDLE IT:
    Pair of 3-500z tubes, 300 watts carrier.
    About 1/3 power output of the total plate dissipation.
    That would be about 1200 watts pep if everything is working well.
    150 watts for one 3-500z.

    The duty cycle is high, and at that power level on AM, things like traps and baluns blow out in short order, coils melt, RF can get into things...
    3 or 4 KW is likely easier then 300 watts of AM modulated fully...
     
  10. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Don't know about the midwest but I hear LOTS of stations here in the Pacific Northwest running 20-40 watts all the time on the local AM nets and they sound good!

    I plan to have my Globe Scout 680, DX-60b and Eico 753 lined up soon to do the same

    Dave
    W7UUU
     

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