Tag: Dock antennas
Standard flag -VS- Dual in-line phased loops (Waller Flag)
You know my previous post where I stated I’d be keeping my Waller Flag until I moved? Well, about that…
The other night I noticed I had lost all directivity on my “Waller Flag” receive antenna. I was unable to troubleshoot the cause, and I checked everything possible – transformers, termination resistors, feedline, ETC. I reconfigured the antenna as a standard flag receive antenna, 16ft high by 26ft long, terminated with a 920 ohm resistor and matched with a 9:1 transformer on the other side. I got my pattern back. This antenna has a fatter front lobe, more gain, better front to back, and seemingly better immunity to it’s surroundings (no interaction noticed). Signals seem to be close to the same strength on this antenna as the transmit vertical, but with less noise. The plot below shows the pattern as opposed to the Waller Flag (in yellow prior to the loss of directivity). You can see the narrower front lobe and better F/S the WF provides.
Deember 2020 update: Please don’t let this dissuade you from trying the WF. In my case, I had interaction issues with nearby power lines that I was not able to overcome. N4IS continued to develop the antenna, and DX Engineering sells a commercial version. JC determined that a horizontal WF, high in the air, outperformed the vertically polarized version lower to the ground, and K3LR has one at his Multi Multi station. The antenna does work!
Dual Phased Flag Receive Antenna (Waller Flag) – More
Here are a couple more pictures showing the updated configuration of my Waller Flag receive antenna. I connected a rotator so I can now turn the antenna from the shack; the antenna seems to be working well enough that I went through the effort of running the rotor cable down the dock.
Here is another plot of the antenna’s pattern:
Power lines run along the shore line, to the left of the antenna in the plot above, about 50ft away. You can see how the pattern is disrupted – reradiation of noise? There is not much I can do about it but relocate the antenna further away down the dock, which would place it directly next to the big vertical. I would have to do a full reconfiguration of all the antennas – which is not going to happen.
So – honestly – how does the antenna work? To Europe I see definite performance. I hear stations on the RX antenna that are inaudable on the TX vertical. In other directions, the receive antenna improves the signal to noise ratio, however there have been several cases where I still hear the DX best on the transmit antenna. I suspect that I hear exceptionally well with the vertical as it is located over salt water, which may make it seem like the RX antenna isn’t working as well as it is. On the higher bands I see definite performance, even on 17 and 15m. On these bands I have a high hoise floor, and the RX antenna definitely knocks the edge off on the noise. I am extremely happy with the Waller Flag, and will keep it until time to pack up and transfer in late Spring 2010 (where to, I don’t yet know).
Here is the rotator showing the home-made heavy duty twisted pair feeder at the high stress turning point.
Waller Flag Receive Antenna – Revisited
Here are two plots showing the antenna pattern. I do not have a rotator – so while plotting I am manually rotating the antenna, trying to maintain an even speed while making one full revolution in 60 seconds. Not easy! This plot was made while listening to AM1600, a low power omni station 2 miles to my east, a clear shot across salt water.
The yellow is with the 160/80m antenna in the 80m position (detuning the antenna from 160m). The blue arc is in the 160m position. There seems to be little difference, with the exception of some lost F/B, however I notice the noise floor increase when listening on the RX antenna and switch the big vertical into resonance on Top Band. Also note the fatter lobes to the left quadrant. I have power lines running on this side of the antenna, perhaps 50ft away. Could this be the reason?
This seems to be a much prettier plot. This was taken while listening to AM1660, located due north of my some hundred miles away on the mainland in Naples, Florida. The difference is that I am looking directly into the power lines when pointed at this station. In my opinion, this confirms that the rear lobe seen on AM1600 is due to interaction with the power lines.
I replaced the CAT5 twisted pair at the point where the mast rotates in it’s mount. The other day, I left the antenna unpinned and it freewheeled in a thunder storm, breaking the CAT5 twisted pair. This beefy homemade twisted pair was made by cutting two equal lengths of wire, and spinning them with an electric drill with the opposite ends in a vice.
Waller Flag Receive Antenna – Another Update
Thanks to Carlos, N4IS, for his continued support, by email and on the telephone.
Today I replaced the coax feeders with CAT5 twisted pair. I ran the wire inside the boom and the mast. This should eliminate most if not all chance for common mode noise pickup on the feed line to the preamplifier, as it’s insulated, and because twisted pair is designed to minimize noise pickup.
Using Polar plot, I was able to collect this table that clearly shows that the antenna is working mostly as it should. I did my best to rotate the antenna by hand at a constant rate. For the test I used a 500W AM station about 2 miles away. There are some small lobes to the rear that is probably interaction with something nearby.
Waller Flag Receive Antenna Update
I spent all weekend messing around with my “Waller Flag” receive antenna.
Some background: I have a remote antenna switch located on the dock right at the shoreline. All coax and control cabling are shielded, buried, and extensively grounded at the antenna switch, both with a ground rod and several radials laid into the salt water itself. From this point I feed all my antennas, both with feed lines and control cables (20m array and 80/160m switching). This setup has served me well, protecting my station and home electronics from damage when the antennas took two direct lightning hits this summer.
For my receive antenna, I ran a new length of coax from the pre-amp at the base of the mast to the ground point where I tapped into an unused coax for the 25ft run to the station. The cable is submerged in salt water for the entire length to try to eliminate common mode currents on the feed line jacket. To supply 12v to the amp, I used a piece of flooded RG-6 coax, with + on the center conductor and – on the braid. I had it laying around, so I used it. This cable was also submerged from the antenna switch box (where I tapped into 12v) to the amp itself.
All weekend long I struggled with the antenna. It did not seem to be working properly. With one AM station I would see 20db+ F/S and F/B but on another I’d see little or no difference. At night, the receive antenna seemed to hear worse than my transmit vertical. I was becoming frustrated.
On a whim, I replaced the 12v power cable with a fully jacketed two conductor cable. I grounded the jacket at three points along it’s length, by connected bare copper wire and laying radials into the salt water. Presto – my daytime noise floor with the amplifier on went from S8 to S5, an 18dB decrease in noise. Last night, for the first time, I was hearing exceptionally well with the receive only antenna. On 160m, G4ZCG was even with the noise floor on my transmit antenna (S9). On the receive antenna, without the amplifier energized, he was much weaker but still perfect copy with no background noise. Later I was able to listen to his conversation with a F9 station on 160 SSB with perfect copy. This example played out through the night. Conditions were flat to Europe, however I was able to copy several on the RX antenna I could not copy at all on my transmit vertical with the QRN. The antenna also performs well on 80 and 40m. JD1BMM on Minami Torishima was solid copy on 40m this morning well after my sunrise. I could not hear him on my 1/4 wave vertical.
So far today I have added two more grounding radials to the control and feel line shields, further dropping my daytime noise floor from S5 to S4. I plan to continue grounding until I see no more improvement, at which time I will add some more ferrite beads to see if I gain anything further.
As a followup, I am seeing some excellent F/S and F/B with this antenna now that I have corrected the common mode concerns. AM1300 in Marathon, Florida, about 45 miles away, is S9 on the RX antenna. Turning the antenna 90 degrees away from the station drops the signal to S4 (30dB if my K3 S-meter is accurate). For a while I thought I had a bad electrical connection – this afternoon I am seeing spikes in the noise level to S9. It turns out that I’m hearing the thunderstorms in South Florida. Turn the antenna away from the storms, and the static crashes mostly go away. Amazing!
New Low Band Receive Antenna (Waller Flag)
I recently finished building a “Waller Flag” receive antenna primarily for the 160m band. The design was taken directly from N4IS’s web site, at which Carlos has published detailed instructions. The design is originally from NX4D, and both he and N4IS have had great success with this antenna.
6M Ready for Desecheo (K5D)
I installed a small, non-optimized, and somewhat resonant 3el 6M beam temporarily to try to work the K5D DXpedition on this band. This morning, I heard a couple CQs from them on 50.106 Mhz but they weren’t copyable long enough to make a QSO. I’ve got a pretty good shot in that direction, as you can see in the 2nd photo.