Re: Topband: Control cable black conductors
Dave G4GED Wrote on Feb. 22nd. Hi and thanks for reading. I'm trying to splice a damaged (rodents) RX ant control cable. It has 7 insulated, stranded copper conductors all inside a PVC jacket. Problem is, when stripped of their insulation, 3 (black, brown and green), of the copper conductors have become coated in a black film? So to effect jointing and soldering, require cleaning. I've tried IPA 170 and several contact cleaners but none remove it. So far, only Emery Cloth will do the job but it's very difficult to clean each strand without breaking some and therefore weakening the joint. All the other 4 conductors are bright clean copper when stripped. Could anyone tell me why some insulated copper conductors turn black in this way and whether there's a better way of cleaning it off. Dave, maybe you could try dilute sulphuric acid or lime scale remover VIAKAL. The black residue on the copper is probably copper oxide. If you end up replacing the cable run then use tined copper conductors. 73 Andrew G8LUG _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Shared Apex Loop Array
Bruce, I have considerable experience with loop arrays; whilst they are good performers in an electrically noisy environment, they suffer from poor directivity at higher angles. This can also be seen with EZNEC models by looking at the AZ Plot with an Elevation angle of say 40 degrees. The directivity and RDF is much better with a pair Phased Flags for example. Other issues, Tom has mentioned a too close element spacing which will lower the array gain. Also there is the issue of array stability i.e. a minor phase or amplitude error will completely screw up the pattern. 73 Andrew G8LUG _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Anyone have a boat load of J-310s?
As far as am aware On-Semi still make the TO-92 J310. Fairchild ceased production about 2 years back. I did a last time buy from Mouser for several thousand J310 and the much more linear J309. 73 Andrew Ikin G8LUG _ Topband Reflector
Re: Topband: Anyone have a boat load of J-310s?
Thirty years ago I used 6DJ8 (E88CC) to solve a third order IMD problem with tuned loop that was using J310s. The IMD was caused by Radio Free Europe on 13m. 73 Andrew - Original Message - From: Charlie Cunningham charlie-cunning...@nc.rr.com To: 'Andy Ikin' andrew.i...@btopenworld.com; 'Topband Reflector' topband@contesting.com Sent: Sunday, August 25, 2013 9:14 PM Subject: Re: Topband: Anyone have a boat load of J-310s? Of course, a 12AT7, or better, a 6DJ8, would be excellent preamps as well, and aren't so sensitive to transients etc. :-) (Showing my age, I guess!) -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Andy Ikin Sent: Sunday, August 25, 2013 3:58 PM To: Topband Reflector Subject: Re: Topband: Anyone have a boat load of J-310s? As far as am aware On-Semi still make the TO-92 J310. Fairchild ceased production about 2 years back. I did a last time buy from Mouser for several thousand J310 and the much more linear J309. 73 Andrew Ikin G8LUG _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: Anyone have a boat load of J-310s?
Charlie, When I was poor man 40 years ago, I always wanted Tektronix 545B Scope, which I couldn't afford. So I built a Chinese Copy with discarded parts from the Calibration department of the computer company I worked for. The scope use many 6DJ8s. I did get it working after about a year; not bad for some one with no formal electronics training Tektronix were very helpful in supplying some critical parts. Looking back I must have been mad, but it was one hell of away to learn how these things work. Bye the way I manufacture a special Head Amplifier for the KAZ and other Flags. This has 1100 Ohm input matching/isolation transformer, about 20dB gain and a less than 1dB NF and uses 8 x J309s plus a string of 1N4148 limiting diodes. Wellbrook FLG100LN. There are about 70 units in service mainly in the US with MW Dxers. 73 Andrew G8LUG - Original Message - From: Charlie Cunningham charlie-cunning...@nc.rr.com To: 'Andy Ikin' andrew.i...@btopenworld.com Cc: 'Topband Reflector' topband@contesting.com Sent: Sunday, August 25, 2013 10:29 PM Subject: Re: Topband: Anyone have a boat load of J-310s? Yes, we could swing the grids of those tubes quite a ways before encountering enough non-linearity to produce a significant amount of intermod, Andy! The old original AMECO tunable vacuum -tube preamp, that I borrowed from Bill, K4CIA, worked really well with my KAZ terminated RX loop for the low bands. It was connected to the receive antenna port on my FT-1000MP, so I wasn't blowing FETs! My electronic design career began before the end of the vacuum-tube era, and I used the 6DJ8 commercially in some VHF monitor receivers, as a cascode RF stage in the front-end. 73, Charlie, K4OTV -Original Message- From: Andy Ikin [mailto:andrew.i...@btopenworld.com] Sent: Sunday, August 25, 2013 5:16 PM To: Charlie Cunningham Cc: Topband Reflector Subject: Re: Topband: Anyone have a boat load of J-310s? Thirty years ago I used 6DJ8 (E88CC) to solve a third order IMD problem with tuned loop that was using J310s. The IMD was caused by Radio Free Europe on 13m. 73 Andrew - Original Message - From: Charlie Cunningham charlie-cunning...@nc.rr.com To: 'Andy Ikin' andrew.i...@btopenworld.com; 'Topband Reflector' topband@contesting.com Sent: Sunday, August 25, 2013 9:14 PM Subject: Re: Topband: Anyone have a boat load of J-310s? Of course, a 12AT7, or better, a 6DJ8, would be excellent preamps as well, and aren't so sensitive to transients etc. :-) (Showing my age, I guess!) -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Andy Ikin Sent: Sunday, August 25, 2013 3:58 PM To: Topband Reflector Subject: Re: Topband: Anyone have a boat load of J-310s? As far as am aware On-Semi still make the TO-92 J310. Fairchild ceased production about 2 years back. I did a last time buy from Mouser for several thousand J310 and the much more linear J309. 73 Andrew Ikin G8LUG _ Topband Reflector _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: Magnetic Loops
Gary wrote on May 21. I've had a Wellbrooke loop for a few years at 20' on a TV rotator. It nulls a single nearby QRN source NW at 300 deg true. EU is about 15-30 deg from here. When 160 or 80 are open over the N Pole, it often helps me hear the weak. It's less effective on multi-source QRN, but still helps at times if I rotate the loop to null the loudest noise and max the received signals. No room for other receiving antennas, and the loop ignores legal limit transmissions on a 120'x120' lot. What more can I ask? 73, Gary NL7Y Gary, Deploying the loop at ground level can sometimes reduce local QRN compared to mounting it high up where it can pick-up noise radiated from sources below. Also it may be prudent to make sure you have mains filter on the rotator, receiver and Loop power supply. Preferable one with a Earth line choke, so it can have a separate ground connexion to the equipment isolated from the powerline Earth. 73 Andrew G8LUG All good topband ops know how to put up a beverage at night. _ Topband Reflector
Re: Topband: Magnetic Loops
Richard Karlquist wrote on May 21. It is important to understand that these loops have a circumference of 10 feet, which they are limited to because the manufacturers want to offer a bandwidth up to 30 MHz. Also, they are untuned, again because the manufacturers want to offer a broadband solution. Very little signal is available from such a small untuned antenna, and hence these antennas require a high gain preamp. Depending on your location, the amplifier noise may be the limiting factor on sensitivity. One of the commercial loops claims to have 0.5 dB noise figure, however I measured 3 dB on a sample of one. These issues are simply physics, no matter who builds the loop. IMHO, a so called Moebius configuration doesn't fundamentally change anything with respect to these tradeoffs. As the inventor of that design states, it is only an advantage for its intended purpose of EMP weapons testing. Rick, The most important limiting factor in regard to sensitivity with a small wideband loop is the loop/amplifier mis-match over several octaves. Any mis-match is equivalent to putting an attenuator in front of the amplifier. Hence, the amplifier noise figure is not a significant factor. That is why Wellbrook use an amplifier that copies the loop element reactance over at least 5 octaves. Where the small loop size is a limiting factor for Topband and MW Dxing, then the large Aperture ALA100 offers significantly better performance, when used either as a single or Phase array antenna. 73 Andrew Ikin G8LUG All good topband ops know how to put up a beverage at night. _ Topband Reflector
Re: Topband: Ferrite core
Rune, Let me have your address of list. I can let you have a few of Fair-rite 2873000302 or 287300202 cores. I can't help you with the large ring core. There is no reason why you can't use the above as a 1:1 isolation transformer to reduce common mode at the receiver ( e.g. 5 turns biffilar 30 SWG). This can be more effective than a choke. Word of warning 73 material is conductive, so you make sure than you use sleeve inside the cores. I will sleeve the cores for you. 73 Andrew G8LUG Wales UK. - Original Message - From: La7tha la7...@tussa.com To: topband@contesting.com Sent: Sunday, July 01, 2012 1:18 PM Subject: Topband: Ferrite core Hey Gents I am currently doing and order from Dig key but I am not able to find binocular core for e.g. beverage transformer etc. I also looking for donut core for Common mode suppression on coax etc, this is only for RX use. 1. anyone that can point me to what type of core is should use? 2.Do Fair-rite send small quantity to private persons? Thanks in advance 73 Rune LA7THA ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Wellbrook receive loop performance
Rag LA5HE wrote on April 9, I put one up last autum and have compared it with my Titanex V160HD . At this quiet location I had to realise that nothing was gained, which was a disappointment ! 73 Rag LA5HE in Telemark Rag, the ALA1530 is not designed to compete with very large antennas like the Titanex V160HD or with other loops with larger apertures. Its primary purpose is to provide low noise reception in a high noise urban environment. The ALA1530 has been providing this sort of service for the past 15 Years. This done by cancelling out the local E -field and providing high immunity to conducted power line noise. Therefore, deploying the loop in a quiet location, the aforementioned features will not be seen. However, if one requires, say more gain or more importantly a higher s/n with a Broadband loop, then a larger loop aperture is required. To this end Wellbrook provides a Medium aperture loop the ALA100M for simple wire loops say 4 to 8m in circumference or the new ALA100LN large aperture loop for 20m circumference antennas. 73 Andrew Ikin ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Pixel Technologies Magnetic RX Loop
Steve WB6RSE, wrote on May 8, 2011 If you've built your own Mobius receiving loop of tried the commercial product, a report of your experience would be of great interest to the Top Band list. Steve, I have just received a recent review comparing the above product to the Wellbrook ALA1530, it can be found at: http://www.wellbrook.uk.com/reviews/ALA1530-vs-RFPRO-1AReview.pdf The review has a link to some MP3 recordings of the s/n comparisons from the LW band up to the 13m broadcast Band 73 Andrew G8LUG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
