This week I completed a couple of antenna projects.  The first was the PA0RDT Mini Whip, which is a small active antenna that you mount on a post high above your shack and feed with voltage through the coaxial cable.  The actual receiving antenna is a small 1X2" section of PC board, which feeds the amplifier circuitry on the same piece of board.  Bill Bradrick, KB0LXZ etched a board for me which he designed for use with surface mount parts.  I didn't have a lot of surface mount parts, so I made it work with through-hole components soldered to the board in a kind of Manhattan style.  The power feed unit I constructed on my own, and housed in a small Radio Shack project box.



The thing about the mini whip is that it just looks too small to be an efficient LF through HF antenna.  Conventional wisdom states that effective antennas must be nice & long, so I was a bit skeptical about its performance even though I have several friends who built them and swear by them.  It turned out my skepticism was warranted.  The mini-whip performs very well for its size.  You wouldn't think a 1X2" piece of PC board could pull in signals very well, but it did.  However, this was only true for strong signals.  Weak signals which I could hear well on my vertical or random wire were non-existant on the mini whip.



Another problem I had with the mini-whip was the introduction of electrical noise.  The amplified mini-whip is very susceptible to noise if you don't get it up high enough.  It may be possible that the weak signals I was missing on the mini-whip were being covered by noise coming from all the electronics in my shack.  I did have the mini-whip temporarily mounted on a pole up 20 ft, but it did not help much.  Of course, the pole was near the end of the shack where all my electronic gear is, so that probably didn't help much.  I think I would probably have better results if I could mount it on a different mast away from the shack.  I'd like to take the mini-whip out to a remote location and test it against another antenna.



I put the mini-whip in storage, but I still needed a way to feed two HF receivers.  I had previously built an HF antenna splitter to feed two receivers, but there was a bit of loss in the system.  I was on the ZIRCNet IRC channel #wunclub talking to Vambo about it, and he had the idea of using a preamp with a splitter to overcome losses and overcome the problems he was having with one receiver's LO mixing with the other receiver.  I didn't have that problem but thought the preamp idea would work great.



I dug out a preamp I had previously built but didn't use in any equipment and decided to use it in this project.  I rewound the toroid transformer to make it split 4 ways instead of just two.  I am quite happy with these results.  I redid the original webpage about my splitter to show this project.  It can be seen at http://www.geocities.com/n2uhc_2/hfsplitter.html.