suggestions for newby

Discussion in 'Amplitude Modulation' started by KK4RSV, Apr 25, 2019.

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  1. AC0OB

    AC0OB Subscriber QRZ Page


    One could start off with a simple acquisition of a DX-60 and an Amp with a Hallicrafters S- or SX- series receivers.

    If one want some middle-weight iron, then the HeathKit Apache TX-1 with the companion Mohawk RX-1 make a good combo.

    The FT-101E also makes for a good hybrid transceiver and with an amp, you can be heard when good conditions prevail.

    Lots of choices out there and it depends on where you want to start and the size of your budget.



    Pheel
     
    Last edited: May 5, 2019
    KK4RSV likes this.
  2. KD6CXW

    KD6CXW Ham Member QRZ Page

    I'm new to AM as well, from a FT-847 were i first used AM to a FT-101 and a Swan mark II amp,and now picking up metal like the Collins 51J-4 receiver and working on real heavy metal a bauer 707 transmitter .
    any one know what the bauer is worth ? it's in real clean shape and will come with lots of extras to put on 160,80,40 meters.
    running a windom offset dipole at 35 feet. works good at lower power but may fry balun at higher power, any suggestions on balun 4 to 1 design or should i go with something different.
     
  3. N2DTS

    N2DTS Ham Member QRZ Page

    Everyone will tell you to use open wire line and a balanced tuna.
    High power AM (anything over 100 watts carrier) has a tendancy to cook/fry/short out things like traps and baluns.
    With some swr, the voltages and currents can go real high.

    I don't use OWL but coax to a balanced resonant fan dipole.
    Takes all the power you can put into it with very little loss and no tuning up, plus you can jump between bands with no antenna adjustments.
     
  4. KD6CXW

    KD6CXW Ham Member QRZ Page

    working on a tower to get me up higher and then can put up different wires and see what will work good for my location.
    I have rolls of RG 6 and use that for the dipole wire and feed it with RG 8.
    If I get the bauer it may need feed with hard line, 75 ohm cable its readily available and should be easy to tune up.
     
  5. W2WDX

    W2WDX Subscriber QRZ Page

    @N2DTS Is correct, to a point. A doublet, OWL and a tuner are great if you over-build them to your power and you need multi-band. Very efficient and low loss if the system is designed correctly. If using it for multi-band, the tuner needs to be wide-range.

    But the same can be said for simple resonant fan dipoles. If you use a balun you should use one rated at least 3X your peak output, so if you are running QRO on AM you need something like a balun rated to 5KW or more. Otherwise it just will not last. Ugly baluns are good, just ugly. I do like a choke balun at the feedpoint on these, since it does keep common-mode off the coaxial. Or at least mitigate it. It's not an issue of matching, it's about choking. If you need to match, you designed the antenna system incorrectly. Flat-top use 75 ohm coaxial, inverted-V use 50 ohm. Good rules of thumb. And measure electrically at the feed-point if possible; very important.

    Right now I'm using a 75M/40M, 117' (longest element) inverted-V fan with feedpoint at 60' fed with a 5KW 1:1 choke balun and Times LMR-400. Works splendidly

    Windoms just do not work out well on AM. I know, tried many. No joy. I was piss weak compared to now, same location same power. I always took out the baluns, total meltdown on a Buxcomm windom rated for 3KW.
     
    Last edited: May 26, 2019
  6. N2DTS

    N2DTS Ham Member QRZ Page

    I do not use any sort of balun.
    Never had an issue or RF in the shack, despite running flex radios and computers along with 400 to 600 watts carrier of AM.

    But whatever works...
     
  7. W2VW

    W2VW Ham Member QRZ Page

    These days baluns on a coax fed antenna should have an advantage of reducing received noise from the world of consumer electronic crap.
     
  8. K5UJ

    K5UJ Ham Member QRZ Page

    Not just any balanced tuna but a link coupled balanced tuna. Link coupled tuna is among other things, a balun. Most hams picture one of those ferrite doughnut things when someone says "balun" and indeed they have their problems, but a link coupled tuna with a tapped down coil and variable caps can be thought of as a variable balun. That network also adds additional harmonic suppression which is important when running one of the old rigs unmodified with a variable link output network (BC610). One problem I have with fan dipoles in snow and ice country is all the loading in an ice storm. Maybe they're okay down in the deep south but I'd hate to have that fan out there all loaded down in the wind and pulling down my supports. Any antenna you put up around here on a nice summer day has to be done with your head in the dead of winter. I try to build in a fail safe, something that will snap and bring down an easy to repair element once the wx action is over, thereby sparing more costly and difficult to rebuild elements of the antenna such as support poles.
     
  9. W2VW

    W2VW Ham Member QRZ Page

    Preaching to the choir and most likely will not change anyone's mind just like religion or politics. but....

    All tuning networks have certain advantages and certain drawbacks.

    IMO link coupling is way over rated.

    I like the Balanced balanced design popularized by Rich Measures in the 90s.

    http://www.somis.org/bbat.html

    They work very well for SWLing and band cruising because they are not bandpass like a link coupled tuner.

    The balun is critical to this design but runs at 50 ohms non-reactive which is a huge advantage over the popular but often substandard hambone T network designs.

    The coaxial "ugly balun" is not going to work well over all of HF but can be OK for 2 or 3 bands.
    A stack of ferrite cores can work just fine even at QRO.

    Another advantage is those of us without lots of land can get on 160 during the winter when 75 is long instead of complaining.

    A full sized doublet just isn't necessary but this trick takes extreme care and lots of copper. There's no appliance solution.

    Non appliance is a great filter. Build one or get back under the porch.

    Fan dipoles are just wonderful if you live in a regular neighborhood. You can make the property look weird which keeps most people away. All the adjustment will insure plenty of sunshine and exercise for the installer. What ham doesn't need that?

    I get a big kick out of people who use a T network to touchup their fan dipoles. Right up there with people who "design" a high power amplifier with a roller inductor because they can't do the simple math.
     
  10. K4KYV

    K4KYV Subscriber QRZ Page

    If OWL is properly balanced, the noise pick-up is no worse than with co-ass. Noise comes in to the receiver via common-mode, which may occur with both types of line.

    Getting rid of common mode usually requires trial-and-error, for example, installing an effective ground at the receiver, and then to try out grounding and un-grounding the frame of the split-stator capacitor in the tuner, and sometimes it makes a difference (sometimes better, sometimes worse) whether the chassis of the receiver is grounded when coax feed is used. What can be perplexing is when grounding the tuner or the receiver helps on one band, but makes it worse on another band. As I recall, Rob said he installed a small knife switch on his Johnson Matchbox to ground or unground the capacitor.

    I had a problem with 40m when I moved the station to the separate shack outside the house, with RF all over the place and excessive noise in the receiver. The wire lead to the earth ground outside the shack is about 7-8 ft long, which was no longer at RF ground potential at the end that connects to the transmitter cabinets inside. I fixed it by running several quarter-wave (for 40m) radials under the floor of the 24' X 32' building, stapling the wires to the floor joists. Two or three run straight, while a couple of others are bent to fit the space, and they are all soldered to a piece of 3" wide copper strap used to ground all the transmitter cabinets. That completely eliminated the RF hot spots in the shack, and the electrical hash on 40m was reduced.

    An RF ground connection is a true earth ground only right at the ground rod or the common point of the radials. I also have about 3 buried radials, each 50' or so long, attached to the top of the ground rod. Ideally, I would run a heavy copper wire or strap round the entire perimeter of the building, with evenly-spaced buried radials connected to that, but have never gone to the trouble to do the work. That would add some lighting surge protection as well as RF grounding.

    As for lightning, due to the rapid rise and decay time of the lightning surge, it should be treated like RF, not like DC or 60~ a.c.
     

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