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Advertising Index ADM Instrument Engineering......... 5 Altronics.................................. 80-83 Dimitech....................................... 21 Elcomtel..................................... 103 Embedded Logic Solutions.......... 99 Emona Instruments...................... 61 Front Panel Express....................... 7 Grantronics................................. 103 Hare & Forbes.......................... OBC High Profile Communications..... 103 Instant PCBs.............................. 103 Ask SILICON CHIP . . . continued from page 102 conductors. If the circuit were prone to failure, that would be a good test. For extra protection in this circuit for the Jacob’s ladder we added a 16V zener diode across the 7555’s supply. That zener was only included due to the much higher coil discharge. VHF antenna for Band 3 reception With the imminent switch-over to digital TV in our major capital cities this year, some readers may not be aware that after this the Government’s digital dividend will result in re-stacking the television channels to band 3 (VHF), at least for the major capital cities. In May 1986, Leo Simpson and Bob Flynn presented an article in the old EA magazine for a high-gain Yagi antenna for Channel 28, something that I built and had great success with in capturing transmissions from outlying country areas from Melbourne. Currently, this antenna is used to receive Melbourne digital TV as well as DAB+ radio and it still works well. I was wondering if SILICON CHIP could do a similar project especially designed to operate in band 3 for channels 6-12. From my perspective, I can’t wait to eliminate the directors no longer required to receive the old analog channels such as ABC 2; the pigeons would need to find a new home! (A. P., North Sunshine, Vic). • We covered this topic last month. The problem with describing DIY antennas is that the cost of aluminium rods etc is so expensive that by the time you buy all the material and 104  Silicon Chip DOWNLOAD OUR CATALOG at Jaycar .............................. IFC,49-56 www.iinet.net.au/~worcom Keith Rippon .............................. 103 WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305 Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au LED Sales.................................. 103 KitStop.......................................... 10 Low Energy Developments........ 103 Microchip Technology................... 23 Mikroelektronika......................... IBC hardware required, it is cheaper to purchase the finished antenna. As a bonus, it will be fully anodised and should last for many years. Having said that, there is probably nothing to stop you from modifying an existing wide band Yagi by removing the long directors and reflector needed for channels below Channel 6. The folded dipole would need to be reduced in dimension as well. A photo in last month’s article showed how an existing antenna would need to be modified. However, unless the antenna was in quite good condition initially, trying to modify and refurbish it could be a lot of time and effort. CFL & LED flicker with solid-state relays I have a home with several homeautomation solid state relays (SSRs) with low-voltage DC inputs switching 230VAC and these have been operating for several years with no issues with incandescent globes. However, whenever I try to put in CFL globes, all “flash” at about two cycles per minute which is not ideal; so I am stuck with incandescents. Recently, I purchased several Osram and Philips LED globes and tested these. The Osram ones do not flash but the Philips ones do flash, so my question is, is there anything I can add (eg, a capacitor) to prevent this from happening either on the DC or Ocean Controls.............................. 9 Quest Electronics....................... 103 Quick Thinking Pty Ltd................... 7 Radio, TV & Hobbies DVD............ 93 RF Modules................................ 104 Sesame Electronics................... 103 Silicon Chip Binders.............. 95,103 Silicon Chip Online Shop........ 96-97 Silicon Chip Subscriptions........... 73 Syndetic Pty Ltd........................... 59 Tekmark Australia........................... 6 Wiltronics........................................ 8 Worldwide Elect. Components... 104 (more likely) the AC side? I prefer the Philips globes as they give a warmer output than the Osram. I also have 12V garden lights (LEDs) that operate via one of these SSRs and a transformer and they also flash but at a slower rate; every three seconds. I would rather not use relays as I don’t see the need in this day and age. I just thought you may have some suggestions how to overcome this. (D. H., via email). • It is likely that the SSRs have a minimum operating current and the CFLs and LEDs may be close to that current and thereby cause them to flash. That is why incandescents with their higher current are OK. Apart from increasing the load current, nothing can be done to cure the problem. SC siliconchip.com.au