Flexradio and OCF 80-6m multi-band (Windom) - thoughts/experience?

Dave - N6XVZ

Inside the fence is a great idea.  However half the fence has metal poles (Vertical) supporting the wood fence.  The other half is community stone wall...  Seems both would mess with the wave being emitted...

Mark WS7M

Dave,

You've got a lot of help here.  I'll chime in again:

1) Inside antennas: you will be disappointed.  It will be a lot of work to put in the attic but in the end it simply will not work as you hope.  You will certainly hear stuff you will be unable to work.  Plus you will likely create lots of RFI in your home.

2) OCF dipole.  These work great but like any dipole the feed line is pretty visible as it will hang down whether it is OCF or center feed.  You also will probably need a balun up there so that makes the connection point look bigger.

3) EF antenna:   Above I pointed you to their site.  With this antenna you can run your coax feed ON THE GROUND, mount the end point of the antenna (with the matching box) on a small stake like 1 foot above the ground then the wire from that box can go up to a tree so it runs like a sloper.   These antennas work very well but like any multiband wire antenna they are a compromise but when faced with needing to be invisible as long as you can get the far end of the wire pulled up and over a tree I seriously doubt anyone will see this as all the bulky connections are mostly on the ground.

4) Vertical:  I realized I have a ham neighbor just a block away.  I never knew it and I drove by his house probably a hundred times.  He has a flag pole with a US flag flying.   I found out that flag pole is his vertical!     Late at night when other neighbors were sleeping he buried 16 radials from the center point of his flag pole.  One neighbor asked him about the dug up strips and he simply said his sprinkler system was having issues.  The guy nodded and walked on.  He buried his coax and a multi-wire shielded cable.  In a hole at the base of the antenna he put in a small utility box with an MJF auto tuner in it.  When every thing was said and done the thing looks like a flag pole.  He can tune it on all bands and says it works quite well.   I  know of NO HOA that can legally prevent you from installing a flag pole.  If done right you have a completely invisible multi-band antenna.

5) One last option.   A tuner feed long wire.   The idea behind this is to have a nice auto tuner probably connected to your house. The wire comes out of this and is connected to a rope and a pulley system in a tree.  During the day or when you don't want it seen you loosen the rope and lower the antenna to the ground.  In the eve you pull it back up.  I even knew a guy that had an automated motor to do this when he wanted.

Basically any of these "outside" antennas will work FAR better than anything on the eves or inside your attic.  When going stealth on antennas it takes more work to hide them but it can be done.  The flag pole is probably the most hidden antenna you can get.   And if some one questions why you are digging a trench from your flag pole to your house you tell them it is to get power to your small lights that will shine up at Old Glory!

Mark

szawrotny

Mark WS7M

Hi have to agree with this completely.  I make no claim the EF antennas work as well as OCF.  The only difference is hide-ability as the feed line from OCF will have to come down some point off center of the wire.

The EF antenna certainly will work WAY better than his original idea of an attic antenna.

It all comes down to what he wants to do, how much effort he wants to put in, and the realization that most antennas are a compromise in some way or another. 

But I totally agree Stan.  OCF way way better.   EF way way better than attic.  

Mark - WS7M

szawrotny

True. That can be mitigated a bit if you keep in mind that only the short side of the antenna actually radiates. The loss might not be that great if you can position it well. And I'm not sure the vertical poles would hurt too much. The stone would block the signal in one direction (broadside).

szawrotny

I agree about the EF being easier to hide because the lead-in is at the very end rather that conspicuously dangling from the center, especially with a big white balun in the air (see my QRZ page - K4SBZ)

Stan

Ken - NM9P

??? Only the short end of an OCF dipole radiates? Where’d you get that? The OCF is simply a standard half wave at its lowest frequency, but since the feed is at the 1/3 point, (or 20% or 40% depending upon the particular design) the feed impedance is at anywhere between 200-600 Ohms. Not only for the fundamental frequency, but at most of its harmonically related bands. This is why the 4:1 (or sometimes a 6:1) current Balun is required. The balun enables the antenna to be matched at the higher impedance feed point on multiple bands...something that a Center fed dipole cannot do.

The whole antenna is active and radiates. The main differences between the two are:

1) feeding at a higher impedance point with a suitable balun allows multiband operation.

2) being an inherently unbalanced antenna, it also requires good feedline isolation to prevent common mode radiation in the shack, and common mode feedline currents disrupting the radiation pattern.

I have made my own OCF dipoles, using a Balun Designs 4:1 balun (about $75). I have used them as 80 and as 160 Meter dipoles, requiring only swapping the short section (45 ft.) of the 80 Meter Version for a long section (180 ft) to make it a 160 dipole. The 90 ft section stays the same — being the long section when designed as an 80 meter antenna, and becoming the short section when designed as a 160 meter antenna. (These measurements are approximate, subject to tuning). The antenna(s) have performed superbly for several years, being transformed several times for seasonal needs, in order to accommodate other antenna projects in my limited space.

I certainly agree that it is more economical to build your own. BUT...my first experiments with an OCF dipole were dismal, because I did not use a 4:1 balun, and the impedance mismatch killed its real usefulness.

The thing I first noticed with a proper design was how much better it received on the harmonic bands than a Center fed dipole. At the fundamental frequency they were both great, but the difference when going to the higher bands was staggering...

But taming the common mode RF was a little challenging until I wound some coaxial “ugly baluns” at each end of the coax. Problem solved...at least at low power.

Mark WS7M

Dave:  

Your specific questions:

1) 4 feet from brick - I think this will be better than anything in the attic.  I think you need to presume you will have to try something, so best not make it permanent until you have tried it.  You may need to make small adjustments or even re-position stuff.

2) Eye bolt and brick veneer.  Bungees work well but require replacement about yearly.  There is a guy selling these shock absorber type things for wire antennas but when I looked at them they were fairly large and quite visible.   Once again I suggest you start with bungees and adjust as you learn more.  You might have to rehang things a few times but you will eventually figure out something that works.

3) For me, height = good.  The higher the better.  This is why Remote Ham Radio, as an example puts even dipoles up at 100 feet when they can.  But you will have to work with what you can.   One thing for sure:  9 feet outside is better than 50 feet in an attic.  Again, give it a try, adjust and perfect.

Mark

Rick N4RZ

Dave, outside antennas, and generally speaking the higher the better, are the way to go.  But, if that turns out not to be possible, an attic antenna can work wonders.  W9BS lives in a condo in south Florida and works all HF bands 80-6M very well with an antenna in the attic.  His antenna is an 80M dipole with two 90 degree bends in each leg fed with 33' of 450 ohm window line.  (See his qrz.com page for additional details)   We have a weekly sked on 75M SSB with some of us over 1000 miles away and his signal in most cases is equal to or better than others using outdoor antennas in the same area.   The antenna works on other bands as well since he has used it to accomplish 5 Band DXCC and needs 1 more state for 5 Band WAS.  

Dave - N6XVZ

I'm thinking not only the 4:1 but also a 1:1 RF choke between the balun and the coax feedline to keep things out of the shack.

Dave - N6XVZ

I reality the brickwork is on the bottom part of the antenna so I should be ok as it's outside and better than inside and various electrical shields/interferences.  

As of know I've submitted my plans to the HOA.  I have a mockup of it built via paracord across my yard and with the black cord approximately the black antenna I'm planning on using, it is amazingly hard to see unless you are in my yard looking at it.  I'm situated in such a favorable position (no neighbors to the west of my house where antenna will be) and only the HOA pool/grass area there with their/my trees between it can't be seen.  I am on the board but have to obviously recuse myself from the decision.  I think they are very reasonable and am hopeful for approval in the next few weeks once the discussion occurs.  

Thanks again for all the great feedback and thoughts.  It helped me refine what I wanted to do.

Dave - N6XVZ

Rick- good points and will be my fallback if I can't sway the HOA.

It's really my major hurdle - no sense buying a radio if I can't get it out.  Of course I have many options still.....  Oh then I gotta start studying for my General ticket!

Dave - N6XVZ

FYI - Making progress with HOA.  Heads are nodding and no one is flinching.  I'm expecting written approval in the next week or two!

Dave - N6XVZ

FWIW passed my General and HOA approved the antenna. Score one for the good guys! Thanks again all.

Ken - NM9P

Well done!  Congratulations!

W1MSG