Dave, W1HKJ, has just announced the latest versions of two programs comprising NBEMS (Narrow Band Emergency Messaging System.) Fldigi 3.0 is a user friendly general purpose multi-mode digital communications program that handles a broad variety of digital modes -including several new ones; Thor, MFSK32 and MFSK64. Flarq 4.0, a very easy to use error-free file transfer program using ARQ has also just been released.  Both programs run under Windows 2K, XP and Vista as well as under Linux.  Check it out at w1hkj.com.

Tim, N4um

Dave, W1HKJ, has just announced the latest versions of the two programs comprising NBEMS (Narrow Band Emergency Messaging System.)  The two programs are Fldigi 3.0, a very easy to use multi-mode digital communications program and Flarq 4.0, an ARQ based error-free file transfer program that works in conjunction with Fldigi 3.0.  Fldigi has been designed from the ground up to be both flexible and user-friendly.  The latest version of Fldigi includes several new modes, Thor, MFSK32 and MFSK64.  Both Flarq and Fldigi will run under Windows XP, 2K and Vista as well as Linux. Check it out at w1hkj.com.

Tim, N4UM

You have made your total antenna length (150 feet) longer than a quarter wave at the desired operating frequency.  This is both good and bad.  

It's good because the radiation resistance of a bent quarter wave is considerably less than 50 ohms so it would be a fairly bad match for 50 ohm coax.

It's good because you've raised the radiation resistance of the antenna by making it longer than a quarter wave and thereby improved its efficiency.  

It's bad because you've introduced additional inductive reactance by making the antenna "electrically long."  It's NOT resonant - but that really isn't a problem.

The solution is to cancel out the inductive reactance  while maintaining the radiation resistance close to 50 ohms.  You can do this by installing a capacitor in series right at the base of the vertical portion of the antenna.   This can be a variable capacitor if you wish to range over a substantial portion of the band or a fixed capacitor if you're satisfied with less bandwidth.

I have several antennas deliberately made somewhat longer than a quarter wave length.  On each I use a good piece of RG-8 as a capacitor to tune out the excess inductive reactance.  RG-8 is a lot cheaper and more weatherproof than a decent variable capacitor.  I first simulate each antenna to get some idea of the amount of capacitance needed by using the demo version EzNec - an antenna modeling program.  This gives me a ballpark estimate of the required capacitance.  RG-8 typically has a capacitance of about 30 pf per foot.   After you've estimated the required capacitance cut your piece of coax (a bit on the long side of course.)  Fasten one side of the coax to the feed point and the other to the base of the antenna.  

My understanding of the term "inverted L" is that it specifically refers to an L shaped antenna that has deliberately been lengthened beyond a quarter wave in order to increase its efficiency and raise the point of maximum antenna current higher in the air.  I always refer to quarter wave antennas that have both vertical and horizontal wires as "bent Marconis."

It seems most hams use the term "inverted L" to refer to the shape of the antenna without regard to itslength...another common example of language usage destroying precision.  LOL.

Howard:

I've been running verticals mounted on my dock over salt water for a number of years.  The system I use is relatively simple and seems to work pretty well.  

I use a sheet of copper about 2 by 10 feet down in the water under each of my verticals.  This may be unnecessary according to a number of other posts on this subject - but it makes me feel better anyway!

I run two radials in opposite directions stapled to the underside of my dock.  My verticals are monobanders so I run a set out from the base of each vertical.  I use this kind of system on 40 and 30 meters.

My son (K4RUM) also lives on salt water and uses a SteppIR vertical for 40 thru 6 meters.  In his case, the dock is fairly high off of the water - about 5 feet.  (His last dock got trashed in a hurricane so he replaced it with a higher one.)  He also uses a big sheet of copper down in the water directly below the SteppIR.  When initially installed without radials, the SteppIR exhibited a decent SWR on 40 but matching on 30 and higher was difficult.  To rectify this, we installed a pair of radials for each band stapled to the underside of the dock.  We actually made each pair of radials slightly shorter than a quarter wave...more like .2375 wavelengths.  We ran the radials in straight lines where possible but a number of them had bends in them etc. This dramatically improved the SWR on thie higher frequency bands but I have no way of knowing whether or not the antenna actually radiated any better.  Since we had a coax run of about 250 feet any decrease in the SWR would be expected to have a significant improvment.

I run a sloped base fed, base loaded wire on 80 with the feed point out on my dock.  I have no radials on this antenna (only the ubiquitous copper sheet in the water beneath it).  It works very well.  I use a similar antenna on 60 meters with good results.

On 160 I use a bent Marconi.  The vertical section is 40 feet long and mounted on a piling on my dock - again with only the copper sheet beneath it.  The horizontal section is 95 feet long.  It also works quite well with no radials.

My experience has been that radials don't seem to be necessary on the lower frequencies where the height of the vertical above the water is relatively small in terms of wavelengths but that they are of some benefit on the higher frequencies where the height of the vertical above the water is substanial in terms of wavelengths.  I suspect my obervations may not jibe with predictions made by those who are more knowledgeable in antenna theory but they seem to work anyway!

BTW I've had very good luck using Davis RF's Buryflex coax around and under saltwater.  At a previous location I had about several pieces of it about 50 feet in length submerged to a depth of about 8 feet for several years with no apparent degradation in its proprties.  They make good stuff.

In any case, play around with things and see what happens!

Most MFSK-16 operation is a few khz above the psk31 areas on the different bands.  It is far more robust than psk31 although a bit harder to tune.  

Mfsk-16 and Olivia 16/500 (another robust mode) are about the only digital modes you'll find on 80 meters in the summer months when qrn is high.  Most of the mfsk-16 and Olivia 16/500 operation on 80 is between 3580 and 3585.

I'd seriously consider a vertical - something like a Hustler 6-BTV decked out in camo paint, particularly if you're interested in DX.  You sound like you have a lot of room to put in a decent system of radials on the relatively large piece of property you have.  The vertical - with a decent radial system under it - would probably work better for DX than any horizontal antenna you might be able to erect under 20 to 30 feet.

I installed one once for a friend in a small patch of pine trees and it blended in so well you couldn't even tell it was there.  We ran approximately 100 60 foot radials (overkill I admit) and it worked very well.  Bandwidth on 80 was pretty narrow, better on 40 and fine on 30 and above.

You might also want to consider a flagpole vertical (perhaps fed at the base with an autotuner).  Again, consider taking advantage of your relatively large lot by installing a decent radial system and you should be able to make a vertical do a good job.

I briefly lived in a first floor apartment about 7 years ago and had good luck with an indoor loop thumb tacked about 7 feet up on the walls.  The loop was approximately 30 by 15 feet and I fed it with about 6 feet of 300 ohm TV ribbon connected to a small antenna tuner.  I operated exclusively using CW and the digital modes (mostly psk-31) and ran between 10 and 20 watts.  I certainly wasn't a DX king but did manage to have many decent digital rag chews on 20 and 40 meters.  These days I'm in a better setup but I still work many stations on the digital modes that are using indoor antennas and modest amounts of power.  If you haven't played around with the digital modes, you might be pleasantly surprised at how well they can work with very modest antennas and power levels.

After sitting and listening for hours to VP6DX working Europeans only (which apparently includes South Americans,JA's  and everything else except W's and VE's), I give up.  If they don't want to work me, screw em!  I can understand them taking ten minute breaks to listen for only specified parts of the world, but not for hours on end.  Frankly, they really piss me off!  I've wasted too much time listening to "CQ EU only."  If you feel the same way I do, please go their website and let them know how you feel about it.

Consider getting a used Hustler 4BTV/5BTV/or 6BTV.  Install it on the ground in as clear a spot as possible.  Put as many radials on it as possible and make them up to 30 feet long (if possible).  Their length is not critical since they'll be on the surface of the ground or just beneath it.  I've had success with this kind of setup with as few as 8 or ten radials varying between 8 and 16 feet long.  I concur with some of the previous responses you've received about the inadvisability of mounting a vertical on your chimney.  Chimney's are expensive!  The bandwidth of these antennas is only about 60 khz on 80 and about twice that on 40 meters.  They're pretty broad on the higher bands.  They're inexpensive and are extremely well built.  You can adjust for minimun swr on each band at whatever point in each band that you decide upon.  Just rememebr to start with 10 meters first then 15 etc. etc... working your way downward in frequency.  Have fun.

Mike:

I've been using several verticals mounted on dock pilings in my salt water canal for a number of years.  I use sheets of copper flashing down in the canal for ground plates.  The sheets are about 2 by 10 feet.  The bases of my verticals are about 3 feet above the water level.  I don't use radials on these verticals and they work extremely well.  At one point I had individual verticals for 160, 80, 60, 40 and 30 meters but got sick of putting them up and down for hurricanes.  I've replaced the verticals for 80 and 60 with base fed, base loaded wire slopers running from the dock pilings towards the top of my tower.  I now use an inverted L (actually a bent Marconi) on 160 with a 40 foot vertical section and a 90 foot horizontal section. It'll come down well before hurricane season and won't go back up until next winter. I can't believe that the performance of my verticals would improve by the addition of radials.  I tried it once on my 40 meter vertical and nothing really changed.  I've done some QRP operating from my small sailboat and have not used radials.  I simply take along a piece of copper flashing about 6 inches wide and 8 feet long and drop it over the side when operating at anchor.  My insulated backstay works like gangbusters with this setup.

Tim, N4UM

The open wire or ladder line center fed 130 foot wire will be easier to tune on 160 if a loading coil is added about 10 feet from each end.  Use a 2 inch diameter piece of PVC with about 50 or 60 turns of wire on it.

Try it!

A 100 foot piece of wire fed in the center with low loss commercial ladder line or home made open wire transmission line should enable you to operate from 3.5 to 30 Mhz.  You will need an antenna tuner to keep your transmitter happy by enabling it to operate into a matched load.  A wire about 30 feet in the air should provide you with a low cost antenna that will enable you to make many contacts.

A horizontal loop around the perimeter of the garage fed with ladder line should work fairly well for you. I used a similar antenna inside a small apartment. It was 8 feet above ground level. My loop was about 30 feet long and 12 feet wide.  I was able to make a fair number of contacts with it on 30 meters and above. I'd recommend that you consider getting on PSK-31 if you have a computer available.  That mode worked very well for me running about ten watts to my indoor loop. I work lots of stations on PSK who are in restricted settings and they seem to have good luck with low power and clandestine antennas.

I'd consider putting some 2x6's at right angles to the rafters underneath the roof. Make them long enough to overlap at least 4 of the rafters.  The idea is to distribute the stress from the tower over a relatively large portion of the roof so that it is not all concentrated in a small area.  I think Glen Martin's  advertising brocure illustrates how to do this.