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Effect of antenna height on 21MHz performance at GB2GP

12/30/2020

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The next contest band for HFTA analysis is 21MHz. The GB2GP antennas are either 3 elements on the 100ft tower or 4 elements on either the 80 or 60ft towers.
The graphs below show that the as wavelength increases, height becomes more important to achieve the lower take of angles. the absolute difference between the high 3 element and lower 4 element yagis is less than at 28MHz, but the 4 element antenna at 60ft has better average performance across a wide range of arrival angles, as indicated by the Figure of Merit.

The general terrain at GB2GP has a downward slope in several directions, with the only rise towards the North East - i.e. towards Japan. This is reflected in the HFTA analysis where the extra tower height seems to really help. You can see the general horizon with the screen shot from heywhatsthat.com below.

On 21Mhz, a lower antenna may be better overall, but my conclusion is that this band will not see any major improvement by moving antennas around.

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Effect of antenna height at GB2GP on performance at 28MHz

12/27/2020

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GB2GP has three towers at 60, 80 and 100ft. For 28MHz we currently have a 3 element yagi at 100ft, a 5 element yagi at 80ft, which could be moved to the 60ft tower if needed. There is no easy way to move the big yagi to 100ft.
The HFTA analysis presented in the gallery below compares these antennas against a flat earth model. I have assumed the following beam headings:
JA - 30 Deg
EU - 80 Deg
AF - 170 Deg
NA -300 Deg
SA - 235 Deg
AS - 80 Deg
Click through the gallery and let me know which height would would choose and why!

My conclusions at 28Mhz are:

1) Gain is more important than tower height at this site on this band.
2) The 5 element at 28MHz has a better figure of merit at 60 ft in most directions as it's gain doesn't fall away at medium arrival angles compared to higher antennas.
3) The take of angle to the EU is quite a lot more than 5 degrees, maybe EU isn't DX?
4) My on air experience is that the 3 el at 100 ft is able to open the band. I guess this is because the arrival angle is low and the combination of 100ft tower and the slope works to our advantage.

Please use the comments below or tag me in Twitter!

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A study on the effect of terrain on your antennas

12/27/2020

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A popular YouTuber was speaking recently about how we should use vertical antennas to “command DX” as their primary lobes are at low angles, he uses gain at 5 degrees to promote the antennas we sells. This reminded me of some work by N6BV published in the ARRL Antenna Handbook which demonstrated that your terrain also has a substantial impact on the lobes of your antenna. This led me to consider what the effects of the terrain at GB2GP has upon on the performance of our antennas.

There is nothing new here; N6BV created some modelling software called HF Terrain Analysis (HFTA) which plots the gain of typical horizontal antennas over your specific terrain and can compare it to flat earth. We are pretty lucky that Gilwell Park is on a local high spot so it will be interesting to see how the slopes that are in several directions have an impact.

The image below is a typical HFTA output and compares the gain of a 3 element, 28MHz yagi at 100ft over the terrain at Gilwell Park (blue line) beaming to north America, compared to the same antenna over flat ground (green line). The terrain give a clear advantage at 2 degree take off angle, +7dBi, but a 2.5bDi disadvantage at the 5 degrees.

Generating the terrain profiles for HFTA) has generally been a serious undertaking, but luckily K6TU has done us all a great service by automating this on his website https://k6tu.net/?q=TerrainProfiles. I have used these and thank him for making these publicly available.

Antenna height has a substantial impact on take of angles for horizontal antennas and we are fortunate at GB2GP to have three towers for HF yagis at 60, 80 and 100ft. Would swapping the antennas round offer any significant advantage on any particular contest band? The following posts simulates our current antennas at each height in key directions.

HFTA also includes take off (or arrival) angle data for signals over specific paths. Whilst 5 degrees cited in the opening paragraph might work as a rule of thumb, it’s a long way from the full picture as the Angle of Arrival changes with ionospheric conditions and HFTA plots the percentage probability of different arrival angles on a second y axis. This data suggests that we all need different antennas to suit every set of conditions, but acknowledging the real world, HFTA also includes a coarse judge of quality that amalgamates the gain over your terrain with the Angle of Arrival profile to help us decide which configuration is best.

The graph below shows the same set of antennas and direction with elevation statistics for the same path. 8% of signals arrive at 2 degrees where our 3 element yagi at 100ft has a terrain advantage, but similar percentage of signals arrive at 5 degrees where we have a disadvantage over flat terrain.

The following posts will show a band by band analysis for GB2GP.

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CQWW CW

11/26/2012

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I am about to move house, so only made a few QSOs in CQWW this weekend, mainly with pacific DX found via the cluster.

I heard one station in zone 27 weakly running a pile up so I joined in the fray to try and work a new band slot. After a while the QRM was bad and I couldn’t hear the DX. I decided to stop transmitting and wait for a “TU” so that I can get stuck in again without causing QRM.

Me: [I’ll wait for a TU before calling again]

DX: comes up from the noise “TU – qrz?”

Me: [too slow to drop my call. I’ll wait for the next QSO to be completed]

DX: “M0BPQ – 599 27”

Me: [How the hell did that happen? Quick! Tx a report] “M0BPQ 599 14”

DX: “M0BPQ TU X1YZ TEST”

So, a valid QSO from my side, but how did he know I was there? He must have been using a code reader of some sort and picked me off the screen?

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More WY209 issues

10/16/2012

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The guys from Wimo have been really quick on email and kindly sent out a new boom to fix my incorrectly packed antenna. This arrived at the Scout site on Saturday. The problem is that the box had a neat cut round the centre and the new boom is bent like a banana in two axes.

I hope the Wimo guys can claim for this from their courier as I need another one!

I took a closer look at the remaining parts to build the last yagi and found two potential problems. One is easy to solve – an element without a hole through it which I re-drilled in a flash. The second problem is not so good. The Driven Element has a tag on one side which I assume is used to align the elements and ensure they are all driven in phase. The problem I have is that I can’t align this DE with the other three in the stack without turning it round backwards! Three of the antennas have the DE tag on the left when the connector is facing forwards, whilst the final one has it on the right. Do Wimo produce the DEs in different orientations? Or has the tag been placed on the wrong side? How do I find out? I can’t use an ohm meter on a folded dipole…. Answers on an email postcard, please

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Wimo WY209 Build and problems

10/9/2012

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I have been buiding some wimo yagis to use for JOTA,but have hit some problems with one antenna. Here are the parts laid out for the two new yagis that I bought. All looks well!

But looking a bit more closely there is a problem with the boom sections. The top pair are OK, with the rear boom section at the very top of the picture and the front boom being the next one down. However the two sections supplied for the next antenna are identical. This photo was taken at the point where the DE attaches. Apologies for the quality of the photos!

So, have I been sent 2 x rear booms? I think not. If you compare the top boom section and the bottom two then holes do not line up. This is at the D1 hole.

I could have flipped the booms through 90 degree and redrilled, but as the picture below shows, the boom sections supplied are too short.

So - I now have three antennas complete, and have written to wimo to solve the boom problem with the third. Let's hope the customer service is good...

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QSO with 8P6DR

10/8/2012

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Working 8P6 is nothing special, but it was nice to get 8P6DR, who is my HWCG club mate -G3RWL. Here's a video of a him working PY some time later!

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WPX CW 2012

5/28/2012

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For the first time in almost 3 years I got the chance to operate in WPX CW. Conditions seemed to be good and I had a lot of fun over the 6 or so hours I was on (in bursts). Over all I made 339 Qs in 66 DXCC without really trying. The most fun I have had on the radio for some time!

Summary of DXCC entities worked by MØBPQ on all bands

Summary of DXCC entities worked during WPX-CW by MØBPQ on all bands
Type of propagation: All Mode: All mode
From 24/05/2012 to 28/05/2012

DATA OF FIRST QSO

DXCC QSO Conf CALLSIGN DATE TIME BAND

4L (Georgia) 1 0 4LØA 27/05/2012 00:10 20 m.

5B (Cyprus) 2 0 5B/RN3QO 26/05/2012 09:07 10 m.

6V-6W (Senegal) 1 0 6V7S 26/05/2012 21:35 15 m.

9A (Croatia) 7 0 9A3VM 26/05/2012 07:43 10 m.

9V (Singapore) 1 0 9V1YC 27/05/2012 00:19 15 m.

A7 (Qatar) 1 0 A73A 26/05/2012 23:32 80 m.

BY,BT (China) 1 0 BY5CD 27/05/2012 20:42 20 m.

CA-CE (Chile) 5 0 CE3CT 26/05/2012 19:59 10 m.

CM, CO (Cuba) 2 0 CO2MS 26/05/2012 22:23 20 m.

CT (Portugal) 1 0 CT2AA 26/05/2012 22:33 20 m.

CT3 (Madeira Is.) 3 0 CR3L 26/05/2012 09:25 10 m.

CV-CX (Uruguay) 1 0 CX2AQ 26/05/2012 20:49 15 m.

D2-3 (Angola) 1 0 D3AA 26/05/2012 21:41 20 m.

DA-DL (Fed. Rep. of Germa) 16 0 DL1WA 26/05/2012 09:14 10 m.

EA8-EH8 (Canary Is.) 1 0 EC8AFM 26/05/2012 20:37 15 m.

EA-EH (Spain) 9 0 EA5AER 26/05/2012 07:54 10 m.

ER (Moldovia) 2 0 ER4X 26/05/2012 21:21 15 m.

EU, EV, EW (Belarus) 3 0 EW8DJ 26/05/2012 09:21 10 m.

F (France) 2 0 F5VHY 26/05/2012 20:56 15 m.

FM (Martinique) 3 0 FM5BH 26/05/2012 20:08 10 m.

G, GX (England) 5 0 GØUCH 26/05/2012 09:49 10 m.

GJ, GH (Jersey) 2 0 MJØCFW 26/05/2012 21:10 15 m.

HA, HG (Hungary) 2 0 HA8RH 26/05/2012 09:02 10 m.

HC-HD (Ecuador) 1 0 HD2A 26/05/2012 20:26 10 m.

HJ-HK (Colombia) 3 0 HK1NA 26/05/2012 20:00 10 m.

HO-HP (Panama) 1 0 HP1WW 26/05/2012 20:11 10 m.

I (Italy) 13 0 IT9BXR 26/05/2012 07:56 10 m.

J3 (Grenada) 1 0 J39BS 26/05/2012 20:09 10 m.

JA-JS (Japan) 3 0 JA8RWU 26/05/2012 21:07 15 m.

K,W,N, AA-AK (United States of A) 97 0 K9CT 26/05/2012 07:26 20 m.

KH2 (Guam) 1 0 NH2T 26/05/2012 21:15 15 m.

KH6 (Hawaii) 1 0 KH6LC 26/05/2012 21:22 15 m.

KL7 (Alaska) 2 0 KL7RA 26/05/2012 21:33 15 m.

KP2 (Virgin Is.) 2 0 KP2M 26/05/2012 19:51 10 m.

LA-LN (Norway) 1 0 LA4DQ 26/05/2012 22:03 20 m.

LO-LW (Argentina) 5 0 LU6EF 26/05/2012 20:18 10 m.

LY (Lithuania) 8 0 LY7A 26/05/2012 09:12 10 m.

LZ (Bulgaria) 10 0 LZ9W 26/05/2012 07:52 10 m.

OE (Austria) 1 0 OE3K 27/05/2012 20:30 15 m.

OF-OI (Finland) 2 0 OG1M 26/05/2012 09:40 10 m.

OK-OL (Czech Republic) 5 0 OL4A 26/05/2012 20:42 15 m.

OM (Slovak Republic) 3 0 OMØWR 26/05/2012 07:32 20 m.

OX (Greenland) 1 0 XP2I 27/05/2012 00:14 20 m.

OZ (Denmark) 3 0 OZ3SM 26/05/2012 23:18 20 m.

P4 (Aruba) 4 0 P49Y 26/05/2012 20:01 10 m.

PA-PI (Netherlands) 1 0 PA3CVI 26/05/2012 23:50 80 m.

PJ7 (Sint Maarten) 1 0 PJ7T 26/05/2012 19:54 10 m.

PPØ-PYØ (Fernando de Noronh) 1 0 PWØF 26/05/2012 20:19 10 m.

PP-PY (Brazil) 14 0 PW7T 26/05/2012 09:29 10 m.

PZ (Suriname) 1 0 PZ5P 27/05/2012 00:08 20 m.

S5 (Slovenia) 9 0 S58MU 26/05/2012 20:52 15 m.

SA-SM (Sweden) 1 0 SJ2W 26/05/2012 21:27 15 m.

SN-SR (Poland) 9 0 SO2R 26/05/2012 07:34 20 m.

ST (Sudan) 1 0 ST2AR 27/05/2012 18:41 15 m.

SV-SZ (Greece) 1 0 SV1BJW 27/05/2012 18:56 15 m.

TK (Corsica) 1 0 TK4A 26/05/2012 08:56 10 m.

UA2 (Kaliningrad) 1 0 UA2FL 27/05/2012 20:43 20 m.

UA-UI1,3,4,6, (European Russia) 14 0 R1DX 26/05/2012 09:40 10 m.

UA-UI8,9,Ø,RA (Asiatic Russia) 3 0 RX9AF 26/05/2012 22:01 20 m.

UR-UZ, EM-EO (Ukraine) 11 0 UR7MZ 26/05/2012 07:29 20 m.

V2 (Antigua & Barbuda) 1 0 V26EV 27/05/2012 19:01 15 m.

VE, VO, VY (Canada) 14 0 VE2OXA 26/05/2012 07:25 20 m.

XA-XI (Mexico) 1 0 XE2S 27/05/2012 18:47 15 m.

YL (Latvia) 4 0 YL2SM 26/05/2012 09:24 10 m.

YO-YR (Romania) 2 0 YO8AXP 26/05/2012 09:27 10 m.

YT-YU, YZ (Serbia) 8 0 YT9W 26/05/2012 07:44 10 m.

66 339 0

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Pan adapter for Elecraft K2

4/20/2012

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_ My Elecraft K2 hasn’t seen the use that it really warrants since I bought it several years ago. With field day approaching in June and the revised rules allowing SDRs and skimmer I thought I would dust it off and try to finally get my software panadapter working.

The set up is fairly simple. A K2 with Z10000 buffer board is attached to a cross country wireless SDR which has been re crystalled for 4.9125MHz. I am using an E-MU 0202 USB soundcard with the SDR, but as my PC is quite limited, I plan to only use it to read 48KHz of spectrum. From a software point of view I would like to run N1MM as my contest logger as well as skimmer and possibly NAP3 as a panadapter. This clearly put some real pressure on COM port usage, as all of those bits of software need access to the K2’s COM port. Fortunately, N8LP has developed LP-Bridge (LPB2) that handles all of this and I am trying to integrate all of this kit together using the information on Larry’s website.

The problem I have now is that it only partially works. Larry’s documentation suggests that one should use Kenwood mode in NAP3 to connect to LPB2 on com port 99. This is where my first problem arises; there is neither com port 99 nor a generic Kenwood setting in NAP3, even when NAP3 is opened first as Larry has suggested to others on the LP-Pan forum.

However, if I close LPB2 and choose Elecraft K2 in NAP3 with the appropriate com port (6 in my case) then I can connect to the radio and NAP3 tracks my VFOs no problem. Similarly, in Skimmer, if I choose IF mode, then Elecraft K2 in the CAT tab, then skimmer connects to the radio and tracks the VFO. The problem here is that I still haven’t told skimmer what my IF out frequency is so I don’t know if that is the correct way to do things.

So a partial success? Clearly I need to get LPB2 working so that I can skim and contest log at the same time. The next issue is that I have a huge spike in the panadapter and skimmer waterfall. I thought the Z10000 should be taking this out? Or have I told NAP3 the wrong IF frequency?

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Free amplifier parts

4/9/2012

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I am sorting out my gear and have two old amplifiers available free to a good home, provided you collect from north London. Both are for 144MHz and are for single 4CX250s. There are two sets of PSU parts, a changeover relay and one blower. One was given to me by a club mate, so is of amateur construction. The other I bought for parts at a rally years ago and is nicely made in a blue case. I was told it was made as a project by apprentices at Marconi, but have no way to verify that. If anyone needs a used valve or two for the project I can raid my box - but you can't have them all. Please contact me by email to arrange collection from North London. Here are some pictures taken in my loft (where the amps have been for almost 6 years - hence the dust!) using my iphone, so excuse the poor picture quality:

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