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Join date: May 24, 2021
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Call sign G4HFS


I was licenced back in 1978 and worked a mixture of SSB and CW (WASCW)

Worked WAB mobile back in the eighties driving to and from work - I used to do over 40,000 miles a year so added interest to the driving.


Most of my base station work was with a sloping dipole and an FT DX 401 in those days - like driving a tank.


The rig nowadays is an Alinco DX 70TH normally at 100 w out, to an MFJ 818 at SWR 1:1.3 max at resonance to a G Whip, 6 band mobile antenna over 40 yrs. old, ground mounted on a ground rod, driven 1.2 metres into the ground with 12 random length insulated ground radials, buried 50 mm deep in the lawn . These only form about 2/3 of a circle, as the house is on the other 1/3. This is a new house and I laid the radials and flexible conduit for the coax before the lawn was turfed. I also use a home brew shunt capacitance box similar to the MFJ 910, using 270pf on 20, 40 and 80. I use CM chokes at both antenna and shack end of the RG 213 - incidentally the "shack" is on the 2nd floor of the house. The base of the antenna is hidden behind a stone sculpture, as shown on the photo, so I can just unscrew the the antenna when not in use - CM choke in grey box. (antenna set for 20 metres in first photo)



As can be seen in the image above a centre loading coil and base extention is used on 160, 80 and 40 metres (40 metres shown above 2.8 metres high)



Pwr supply is from an Alinco DM330MW


This is a new house with a small garden and antennas are not allowed - even the TV sat dish has to be at the back of the house where it can't be seen, so this is my first attempt at a "stealth" antenna, anyway the XYL would object to a Butternut in the middle of the lawn - at my old QTH I had a Butternut HF6V with plenty of land for radials.


The antenna shown above is is helically wound 2 metres high and set for 20 metres. For 15 metres there is a sliding "switch" which isolates part of the top part of the antenna.


The antenna resonates as shown below so is close to Desktop frequency. The Desktop was left running on 20 metres for 24hrs on 10-11/07/ 2021 and was heard by stateside stations, a VK station and all over EU. I did the same on 80 and 40 and was heard by many stations in the EU on 40 and many stations in the UK on 80. This antenna uses centre loading coils and telescopic whip for 160, 80 and 40 including a base extension section on these bands.


I've not fired the rig up yet as I'm still getting the antenna set up and re modelling my shunt capacitance box, as it was last used under a corrugated iron roof acting as a ground plane so it didn't need to be waterproof. Have now re fitted it a w/proof box as above and below photos (excuse the soldering, 81 year old hands are not as steady as they once were)



With regard to the Status LED, I find it "pulses" every 1/2 sec. and when paused every 4-5 secs.


Results of the tests on 20, 40 and 80 with this antenna using an MFJ-259B are as follows.


14.124 R 58 X 9 SWR 1.2:1 (resonant frequency)

14.188 R 78 X 8 SWR 1.5:1

14.054 R 47 X 22 SWR 1.5:1

As can be seen this gives a reasonable band width of 170 khz at a max of 1.5:1 SWR. For other parts of the band I need to use the tuner to allow the transmitter tp see 50 ohms.


7.029 R 39 X 7 SWR 1.3:1 (resonant frequency)

7.043 R 49 X 21 SWR 1.5:1

7.008 R 40 X 13 SWR 1.5:1


3.567 R 38 X 6 SWR 1.2:1 (resonant frequency)

3.572 R 47 X 19 SWR 1.5:1

3.564 R 35 X 10 SWR 1.5:1


With 40 and 80 bandwidth is very narrow, particularly on 80 meteres, however as these bands use a telescopic whip frequency can be adjusted throughout the band and of course I can resort to the tuner for minor tweeking.


Using Zachtek Desktop 80to10, 200 mw, max distance on 40 metres was TF4X at 2,022 km

On 20 metres, max distance was to VK5KJP at 16,290 km. with 25 ststeside stations and 1 VE, including farthest West WD0E near Denver, Colorado at 7,489 km.

Farthest EU stations were OH8GKP at 2,119 km and EA8BFK at 2,759 km.

On 80 metres I managed to connect to GM0UDL at 711 km., F1EYG at 377 km., ON5KQ at 307 km., G0KTN, G8AXA and G3ZIL As this was late morning in the UK, not the best time on 80 meres.

40 metres was similar to 20 metres except for the DX with the farthest East being DK8FT at 950 KM., with OH6BG at 1,843 km., TF4AH at 2,049 km. TF4X at 2,022 km. and EA8BFK at 2,759 km.


Well, to date, using the zachtek Desktop 80to10, I have proved my "stealth" antenna works with good SWR, albeit very narrow banded, as with all these types of antennas, so I will be using my Versa tuner to tune the rest of the band. Yes,I know it only presents 50 ohms to the tranmitter and doesn't tune the antenna.




.

Mel Davies
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