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Atmospherics (merged) (Part 3) |
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#2576 |
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Forum Member
Join Date: Aug 2004
Location: In My Own Little World
Posts: 1,644
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Quote:
....... my antenna is rejecting it but still hearing them on 95.6, 100.7 and 90.7. Lille is there but fluttery and no Belgians! :/
There are some high power Band II transmitters radiating from that site, so do you get any images or de-sense? I know that the inverse square law comes into action (In it's simplest form, you can remember it as "if you're twice as far away from a source, you'll experience it as being one fourth as strong."), but with 5 transmitters running 250kW erp each, I would expect that you may experience a few problems being that close. |
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#2577 |
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Join Date: Feb 2006
Location: Birmingham, West Midlands, UK
Posts: 4,175
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Quote:
Powerplay - Looking at the map of the Isle of Wight, I see that Newport is only about 5 - 6 km from the Rowridge transmitter site.
There are some high power Band II transmitters radiating from that site, so do you get any images or de-sense? I know that the inverse square law comes into action (In it's simplest form, you can remember it as "if you're twice as far away from a source, you'll experience it as being one fourth as strong."), but with 5 transmitters running 250kW erp each, I would expect that you may experience a few problems being that close. I am seriously considering getting a DAB tuner and directional DAB aerial instead of FM. That way vertically mounted I can listen out for Egem. Knowing my luck it's probably on the same frequency as Rowridge DAB. |
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#2578 |
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Forum Member
Join Date: Aug 2008
Location: Between wigan and St Helens
Posts: 1,942
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Quote:
My antenna is a 5 element antiference, horizontal. I was thinking of changing it to vertical so I can get the Belgian stations from Egem that are vertical only.
If I point my Antiference FM 3 at Ireland I can only receive it when I get RDS on the dipole. I am going to make a dipole with a parastic element similar to the the Anti FM 3 dipole for a wider bandwidth. Andy |
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#2579 |
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Join Date: Aug 2004
Location: In My Own Little World
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I am going to make a dipole with a parastic element similar to the the Anti FM 3 dipole for a wider bandwidth.
Andy I've been playing around with one on the 144 MHz Amateur Band and it gives a few dB gain in the forward direction, but if constructed correctly, you can get up to a 30 dB null off the back which for such a simple aerial, is excellent for rejecting strong signals. A few coat hangers a piece of dowelling a choc block and a hot glue gun and in half an hour you a nice little directional aerial. The most important thing is to get the dimensions correct to within 1mm, especially the gap C, as this is critical to obtaining the high front to back ratio. You can make better aerials with higher gain, but given it's size and simplicity the Moxon produces very good results - I'm still convinced that here in London, I heard a Morse id from an Amateur repeater in Scotland in recent lift conditions, so that isn't bad for a simple 2 element aerial. Make yourself a Moxon. Here is a simple design just glueing it to a piece of board. |
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#2580 |
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Forum Member
Join Date: Jul 2005
Location: Sittingbourne, N. Kent
Posts: 310
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[quote=KnobTwiddler;71794189]Have you thought of making a Moxon antenna?
A three element Moxon works well - I've posted details on the Yahoo Skywaves group - plus photos. I use one for vertical reception from Belgium/Holland. It has very good front/back ratio across most of the FM band - the transmitters located at Crystal Palace disappear into the noise as the aerial is pointing to the East (90deg) and the CP txs are at 274deg Now the weather is better I'm going to try a horizontal 3 ele version and see if I can get better F/B ratio than the Triax FM3. Admittedly it needs (A LOT) more work than the simple 2 ele design - but the parasitic director widens out the bandwidth to the full 20MHz. The high F/B ratio of the 2ele Moxon is quite sharp over a narrow bandwidth - but can be over 20dB from 90-106MHz. Design modelled using 4nec2 software. Rgds David Sittingbourne |
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#2581 |
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Join Date: Jul 2005
Location: Sittingbourne, N. Kent
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Quote:
I have to say I am envious of your location David, are you on high ground perchance? Over here on the Isle of Wight, not much to the East to write home about today. Cherbourg is enhanced to the South so my antenna is rejecting it but still hearing them on 95.6, 100.7 and 90.7. Lille is there but fluttery and no Belgians! :/
However I have a clear take-off over the North Sea and East Anglia which covers from around 330 deg (NW) to around 90 deg (E) with just a single ridge 10 km or so from 90-130 deg isn't too bad. It means that weak tropospheric scatter out to 450 km and beyond is common. Closer stations from Belgium and France are there all the time and unless exceptional I don't normally log them. Tropo reception conditions from around 150 deg (SSE) and round aren't anywhere so good - and to get Spain by tropo a while back was exceptional. Actually I'm glad I don't live on top of a hill in this area - I'd probably be swamped with signals and lose a lot of the DX channels. Rgds David Last edited by DDaveBB : 18-03-2014 at 23:11. Reason: addition |
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#2582 |
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Join Date: Feb 2006
Location: Birmingham, West Midlands, UK
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Quote:
I use a vertical dipole for DX Ireland/Holland/Belgium and it works very well I did have 2 dipoles one cut to 88 Mhz and the other 98 Mhz but I only have the 98 Mhz up at the moment.
If I point my Antiference FM 3 at Ireland I can only receive it when I get RDS on the dipole. I am going to make a dipole with a parastic element similar to the the Anti FM 3 dipole for a wider bandwidth. Andy Quote:
My garden is just 8m above sea level and antenna height is 5.5m for a Hor 3 ele on a rotator, agl mounted 9m away from the house. A 3ele vertical Moxon facing East at 6.m agl, and 8m agl for Hor 5ele facing east - these two mounted on a single mast on the house.
However I have a clear take-off over the North Sea and East Anglia which covers from around 330 deg (NW) to around 90 deg (E) with just a single ridge 10 km or so from 90-130 deg isn't too bad. It means that weak tropospheric scatter out to 450 km and beyond is common. Closer stations from Belgium and France are there all the time and unless exceptional I don't normally log them. Tropo reception conditions from around 150 deg (SSE) and round aren't anywhere so good - and to get Spain by tropo a while back was exceptional. Actually I'm glad I don't live on top of a hill in this area - I'd probably be swamped with signals and lose a lot of the DX channels. Rgds David |
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#2583 |
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Forum Member
Join Date: Jul 2005
Location: Sittingbourne, N. Kent
Posts: 310
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Intense Tropo Lift to France/Belgium
The main transmitters from Lille and Egem are coming in at 50dB! Pure FM from Wavre (nr Brussels) is up at 47dB - which is 100km further away than Egem. Duting the day I've had some reasonable tropo reception to the south with French transmitters from Brest, Reims, Charter and Rennes - and south is not the best direction for tropo from my location.
Rgds David Sittingbourne |
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#2584 |
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Join Date: Sep 2011
Location: Norwich
Posts: 1,317
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Yes I am getting Joe FM on 104.1 from Egem and 103.7 from Lille quite strongly so there is abit of a lift. Radio 538 on 102.1 and 102.7 and Sublime FM on 90.7 are blasting in. Shame I've got annual leave next week and it seems the weather is about to turn. It would be interesting to hear if anybody on here is getting any 2m repeater Dx.
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#2585 |
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Forum Member
Join Date: Aug 2005
Location: Whitchurch, Hampshire, England
Posts: 4,323
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Some tropo here this evening too with the Lille frequencies up to 4 bars on the Denon tuner, SE England nicely enhanced (including a pirate, Vibe Essex on 87.5) and Langenberg at up to 3 bars (faded down for now), so some decent signals.
Luckily my usually ubiquitous QRM switched off at about 9.20 pm so I'm able to DX in peace. |
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#2586 |
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Forum Member
Join Date: Jul 2005
Location: Sittingbourne, N. Kent
Posts: 310
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Denmark on tropo at 0730
I picked up Denmark P3 on 91.7 and 97.2 between 0730 and 0747 this morning - better than I had hoped for. (1.7 faded out quickly - but 97.2 was fair for a few minutes.
Reception from northern Germany is quite good as well Rgds David |
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#2587 |
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Join Date: Aug 2008
Location: Between wigan and St Helens
Posts: 1,942
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Quote:
Cheers guys, I haven't heard of the Moxon design before, but think due to the poor location if I did have my antenna vertical it would just overload my receiver (Sony ST-SB 920) with signals from nearby Rowridge and Chillerton. This is why maybe DAB DX could be better for me. Only annoyance would be either you get the signal or you don't, no more faint signals, just garbled break up.
I made a replica of the Antiference FM 3 I did want to make an Anti FM 5 but could not find the measurements for that so stuck with the FM 3 and placed that just above gutter height 2 m lower than the main aerial and the homebrew as I call it performs better than the main aerial as it does not pick up as strong signals as the main one does. So strategic positioning of aerials might help so don't loose hope. Has your Sony 920 have narrow filters in it as I have 2 Sony 311's 1 with 150 150 150 Khz in wide and 110 Khz filters in narrow the other one has 150 110 110 in wide and 110 in narrow I also have a Sony 520 with 3 110's in it that does not have a narrow position. Sutton Coldfield is PITA at times as it weighs in at 59-60 db in flat conditions and last week it went over 75 db and the result was BBC R2 on 87.7 ![]() aNDY |
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#2588 |
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Forum Member
Join Date: Feb 2006
Location: Birmingham, West Midlands, UK
Posts: 4,175
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Quote:
Here I am surrounded by several TX's that hit me with 75db+ signals Holme Moss/Llangollen/Winter Hill/Allerton Park and many others above the 60 db mark but I do well considering this.
I made a replica of the Antiference FM 3 I did want to make an Anti FM 5 but could not find the measurements for that so stuck with the FM 3 and placed that just above gutter height 2 m lower than the main aerial and the homebrew as I call it performs better than the main aerial as it does not pick up as strong signals as the main one does. So strategic positioning of aerials might help so don't loose hope. Has your Sony 920 have narrow filters in it as I have 2 Sony 311's 1 with 150 150 150 Khz in wide and 110 Khz filters in narrow the other one has 150 110 110 in wide and 110 in narrow I also have a Sony 520 with 3 110's in it that does not have a narrow position. Sutton Coldfield is PITA at times as it weighs in at 59-60 db in flat conditions and last week it went over 75 db and the result was BBC R2 on 87.7 ![]() aNDY Or just a mixing of signals?I still want to experiment with vertical polarisation, but it's just the hassle and expense, as I don't have my own ladders and paid a local aerial company to install it last October. It has stood up to severe high winds and just about clears my roof, but as I am not very high, I consider the results a let down. |
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#2589 |
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Forum Member
Join Date: Jul 2005
Location: Sittingbourne, N. Kent
Posts: 310
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Quote:
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I made a replica of the Antiference FM 3 I did want to make an Anti FM 5 but could not find the measurements for that so stuck with the FM 3 and placed that just above gutter height 2 m lower than the main aerial and the homebrew as I call it performs better than the main aerial as it does not pick up as strong signals as the main one does. ..... aNDY I've lost your email address! this web site has all the dimensions for the Triax FM5 http://www.ham-radio.com/k6sti/ just need to work it out - folding the dipole and getting it just right would be the difficult bit but have a look at the "Small 5-element Yagi" - much better front/rear spec than the Antiference/Triax. Rgds David |
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#2590 |
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Forum Member
Join Date: Oct 2010
Location: Grimsby, United Kingdom
Posts: 848
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A nice lift to the West tonight with Pulse 102.5 RDSing also Stray FM 97.2 with RDS
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#2591 |
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Forum Member
Join Date: May 2007
Location: Norwich
Posts: 2,220
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Getting the usual BBC nationals and Classic FMs this morning and last night, and BBC Suffolk is stronger than normal.
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#2592 |
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Forum Member
Join Date: Nov 2003
Location: Art Garfunkel Carpet Warehouse
Posts: 947
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Here in South London, BBC Northampton coming through loud and clear on DAB!
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#2593 |
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Join Date: Mar 2003
Location: Mid-Herts
Posts: 535
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That'll be from the Epping Green transmitter in south east Herts. Nowhere near Northampton
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#2594 |
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Forum Member
Join Date: Jul 2005
Location: Sittingbourne, N. Kent
Posts: 310
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Sony ST-311 Auto-Scan of presets function
I just came across a very useful function on the Sony ST-311 - you can use Auto tune to step through every preset continuously - making it very useful for scanning for SpE
To use it - select "Preset" using the Tuning/Preset button - then select Auto using the Auto-tuning button and finally jog the tuning dial up or down to start it scanning up or down through the presets. If a station is present the scan will stop for 4 seconds before moving on. If not it will jump to the next preset. Apologies if everyone knows this already - but although I've got the service manual I don't have the owner manual so don't now if it is documented. I probably need to adjust the FM muting level as one tuner cuts in on the weakest stations and the other needs a much stronger signal for it to stop on a channel. No such function on the SB920 as a single button chooses "tune"/"preset"/"auto" Rgds David |
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#2595 |
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Forum Member
Join Date: Aug 2005
Location: Whitchurch, Hampshire, England
Posts: 4,323
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Quote:
I just came across a very useful function on the Sony ST-311 - you can use Auto tune to step through every preset continuously - making it very useful for scanning for SpE
To use it - select "Preset" using the Tuning/Preset button - then select Auto using the Auto-tuning button and finally jog the tuning dial up or down to start it scanning up or down through the presets. If a station is present the scan will stop for 4 seconds before moving on. If not it will jump to the next preset. Apologies if everyone knows this already - but although I've got the service manual I don't have the owner manual so don't now if it is documented. I probably need to adjust the FM muting level as one tuner cuts in on the weakest stations and the other needs a much stronger signal for it to stop on a channel. No such function on the SB920 as a single button chooses "tune"/"preset"/"auto" Rgds David |
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#2596 |
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Forum Member
Join Date: Jul 2005
Location: Sittingbourne, N. Kent
Posts: 310
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Small 5-ele Yagi by K6STI
I've just completed construction of the Small 5-ele Yagi from Brian Beezley's website. I've yet to complete the weather-proof housing for the dipole element - which is basically a small ABS box with the element supports mounted on the lid with the box acting as the cover. I tested it out at the magnificent height of 2 metres and the front to back ratio was around 16dB across the band. This figure comes from the dBf readings on the Tecsun PL-380 I used to check it out. It is whole lot better than the apparent 4-5db front/back ratio of the Triax FM3 at the low end of the band. Of course in my urban location reflections off of buildings could be a factor but unfortunately I don't have an open field in which to test it.
I used Stauff insulators and 0.5 inch diameter elements for everything except the driven element as the 0.375 inch stuff is considerably more expensive and mounted on a 1 inch square boom. Modelling using 4nec2 software indicated just a few mm had to be taken off the length of the elements as published to compensate for the larger diameter. I don't have a workshop so it took a lot of effort to ensure the holes were drilled exactly where they were supposed to go - but I got there! When the aerial is mounted on the rotator I'm hoping that signals from the back (Wrotham - 33km / 250kw) will be sufficiently reduced to allow me to use the cheap RTL-SDR dongle without attenuation. Rgds David |
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#2597 |
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Forum Member
Join Date: Jul 2005
Location: Sittingbourne, N. Kent
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Small 5 ele Yagi by K6STI - part 2
The aerial is now in place on the 18.5 ft high pole in the garden - it looks more impressive than the Triax FM3 which is back as spare parts. You can see pictures of this aerial as made by a number of other enthusiasts here http://www.ham-radio.com/k6sti/five.htm with all the details - mine looks identical to the first photo.
I can now use the RTL-SDR with around 7-10dB of attenuation resulting in the loss of very weak signals - so I can catch SpE on a 1-2 MHz wide spectrum. Which is a lot better than previously. I have fitted to clip on ferrite chokes at the aerial feed point to avoid noise pickup on the cable (see the baluns section on K6STI's web-site). Using the dB figures that a Sony SB920 gives - the f/b ratio is around 17dB at 90MHZ around 23 dB mid-band and around 18dB at the top end. A Tecsun PL380 gives 17-19dB across most of the band and slightly lower at the top end. These measurements are hampered by the background noise which is higher than normal, but gives an idea. Basically Croydon stations such as LBC 97.3 drop right into the noise off of the back of the new aerial whereas off the back of the fixed FM5 (26ft high) the signals are strong enough to give RDS. It is also performs well in the direction it is pointed as compared to the FM3 which is not surprising and is pretty much the same as the FM5 which is 6 feet higher, but on the house and subject to higher background noise generally. So lets hope for some decent reception soon. Rgds David Sittingbourne |
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#2598 |
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Forum Member
Join Date: Aug 2005
Location: Whitchurch, Hampshire, England
Posts: 4,323
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Quote:
The aerial is now in place on the 18.5 ft high pole in the garden - it looks more impressive than the Triax FM3 which is back as spare parts. You can see pictures of this aerial as made by a number of other enthusiasts here http://www.ham-radio.com/k6sti/five.htm with all the details - mine looks identical to the first photo.
I can now use the RTL-SDR with around 7-10dB of attenuation resulting in the loss of very weak signals - so I can catch SpE on a 1-2 MHz wide spectrum. Which is a lot better than previously. I have fitted to clip on ferrite chokes at the aerial feed point to avoid noise pickup on the cable (see the baluns section on K6STI's web-site). Using the dB figures that a Sony SB920 gives - the f/b ratio is around 17dB at 90MHZ around 23 dB mid-band and around 18dB at the top end. A Tecsun PL380 gives 17-19dB across most of the band and slightly lower at the top end. These measurements are hampered by the background noise which is higher than normal, but gives an idea. Basically Croydon stations such as LBC 97.3 drop right into the noise off of the back of the new aerial whereas off the back of the fixed FM5 (26ft high) the signals are strong enough to give RDS. It is also performs well in the direction it is pointed as compared to the FM3 which is not surprising and is pretty much the same as the FM5 which is 6 feet higher, but on the house and subject to higher background noise generally. So lets hope for some decent reception soon. Rgds David Sittingbourne Looks good Dave and I'm sure you'll get some excellent results on that aerial in the forthcoming Es season. I have ordered a 9-element Yagi myself, based on Peter Körner's 9.2 design, in preparation for an overhaul of my aerial system. Next will be a rotator and assorted accessories. As I plan to have the 9.2 on top of a chimney-mounted 20ft pole, it will need guying to stabilise it during windy weather. Does anyone here know what sort of costs guying will incur? This overhaul is going to be expensive but it'll be worth it, particularly if it minimises the disruption caused by my ongoing interference problem. |
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#2599 |
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Join Date: Oct 2010
Location: Grimsby, United Kingdom
Posts: 848
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Nice to hear about your antenna David, it looks very nice, do you have a how to build guide that you could link me to as I'd be interested in upgrading from my FM3.
Also do you know if you can do what I have done with the FM3 to the FM5 which is to have both Horizontal and Vertical elements on one boom? Nothing to report DX wise yet, hopefully the Sporadic E season will be starting soon! |
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#2600 |
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Join Date: Mar 2008
Location: Lincoln (Belmont/Waltham TXs)
Posts: 2,344
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Quote:
Nice to hear about your antenna David, it looks very nice, do you have a how to build guide that you could link me to as I'd be interested in upgrading from my FM3.
Also do you know if you can do what I have done with the FM3 to the FM5 which is to have both Horizontal and Vertical elements on one boom? Nothing to report DX wise yet, hopefully the Sporadic E season will be starting soon! You can mount 2 X FM5 (for V & H) on the same boom. This is what John (Skywaves) did, before he used the Körner 9.2 antenna. Cheers, Chris. |
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