Saturday, 30 December 2017
EADELTA 7B Review (HF Delta Loop Antenna by EAAntennas)
I bought one of these antennas at the Lincoln national hamfest from Martyn Lynch. I had bought a 40m OCFD from them before which seemed to work fine, so decided to go for something a bit more expensive. At £200 this antenna isn't cheap, but I bought it for some practical reasons: 1) I wanted an antenna with low noise 2) That would add height to my scaffold pole support (so the antenna would clear my roof line) 3) Multi-band capable as I have a small plot and only one support. 4) Needed something better than my OCFD for CQWW CW contest in 2017. The antenna arrived after an unplanned 3 month wait due to EAantennas not being able to keep up with orders. During the wait I complained to Martyn Lynch who offered a 10% reduction on price, then to EAantennas directly who responded, but failed to get the antenna to me for CQWW CW (It arrived the day after the contest). During assembly I noticed multiple problems: 1) The insulator clamps that hold the elements to the mounting plate are very odd. A clamp in my mind is something with 2 separate parts, these were one solid part with bolts through them. How does this clamp the element? (poor design). 2) The bolts that go through the insulator clamps are just long enough to catch the nut on the opposite side of the mounting plate. After much hassle I ended up flattening the spring washer with pliers to enable 1 turn on adjoining nut (poor design). 3) The balun is secured to the base plate and the element ends to the balun, if the element clamps fail, the elements can rotate and the connection bolts are long enough to short to the base plate (poor design). 4) The elements are too long and heavy for the surface area of the base plate, this means the element clamps are too close together, meaning the antenna is self-detonating in ANY sort of wind. With the antenna assembled I mounted it to the end of the scaffold pole (6m long) and raised the antenna in the sky. Inside I tried the antenna on 10 and sure enough the SWR was around a 2:1 in the cw portion. Jumping to 20m, the SWR was around 1.5:1. Not too shabby! I moved to 30m and used my LDG RM600 remote tuner (directly under the antenna) to bring the antenna into resonance. I was excited to try 30m as my OCFD never allowed me to operate there. I put the linear on and decide to start low at 250w to see how it played (the instructions say maximum potential 1Kw). I made 5x 1min qsos before the SWR started to rise, I could tell straight away it was the balun as after a while to allow it to cool down, the SWR would start behaving again. Maybe the antenna was so far out of resonance on 30m that I could only run 100w there. Oh well, I moved to 40m after an hour or so to let things cool and repeated the above experiment. Unfortunately the same thing occurred. At this point I realised I had bought a pup! The balun was completely useless! Luckily I had a proper 400w 4:1 balun made by GWhip. I went out and swapped out the EAantennas balun and tried the above experiments again and this time no problems (still fine at time of writing). The only downside was that I could no longer tune 30m (2.5:1 swr best case after tuning). The weather deteriorated after a week of having the antenna up and the forecast said 25mph winds. I had my doubts, but the specs said >85mph for the antenna, so I left it up. Big mistake, in what I would call light winds, the antenna started to bend at the base plate. Unfortunately I was at work, so by the time I got home, the antenna was at a 20 degree angle from vertical. I rotated the antenna round into the wind the other way and the wind straightened it up somewhat. What a pile of junk! Totally useless! This antenna is going in the skip (minus the after market gwhip balun, its actually worth keeping as its specifications are truthful and it performs to specification unlike the Delta 7B). Do not buy the Delta 7B unless you live on the moon.