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Announcing the 2019 Utah VHF Society Swap Meet - in a different building The 2019 Utah VHF Society Swap Meet will be held on Saturday, February 23, 2019 at the Davis County Fairgrounds starting at 9:00 AM for the general public and 8:00 AM to allow set-up for those that will be selling. The time is the same as last year - and it is almost in the same location... Same place, different building: At the request of the Fairground officials, the swap meet will NOT be in the same building as previous years, but rather in building #3 - the next building farther south and east of building #2 where we have been in past years. What this means is that you will go past the building where we have been before: If you go into the same building as last year you will likely meet a bunch of unfamiliar people! Remember to renew your membership to see if it is good through 2019 (check the "expiry" list on the "How to Join or Renew UVHFS Membership" page if you aren't sure)and if you do need to "re-up" you may do so in person at the Swapmeet, by mailing a check or using PayPal before-hand to avoid the line. As before, members get in free but there is a nominal fee
for non-members which is $7.00 while the entry for non-member youth (16 and younger) will be $4.00.
If you want to get a table it will be $5.00 additional for
each table, $3.00 for floor space for your own table - this, for
members and For driving instructions and a map to the Swap Meet location, click here. See you next there - and remember to go to the next building to the south!
Considering buying a SocoTran ST-7900D multi-band mobile transceiver? DON'T! Yet another inexpensive Chinese radio has made its way to our shores that, at first, seems like a good deal. Known as the "SocoTran" ST-7900D (Also known as the QYT KT-7900D and possibly under a few other names) it is advertised as a "Four Band" radio - which seems cool, until you see the list of bands:
One of the first things that one should do when getting a new, cheap Chinese radio is to connect it to test equipment to see how spectrally "clean" it is. As is well-known, the BaoFeng and Woxun radios have been all over the map when it comes to spectral cleanliness - even seemingly-identical models from different production runs: Many of the newer-production radios of these brands are "Ok", but outliers are still common. In terms of spectral cleanliness, the ST-7900D is the worst commercially-available radio that we have ever seen! Out of the box, it cannot legally be used on any band except 70cm in good faith! The problem is harmonics: This radio appears to have a single PA (power amplifier) with a single low-pass filter designed to cut off in the 550 MHz range. This filter is probably "OK" for 70cm, but it is completely inadequate for 2 meters or 222 MHz. How bad is it? In one sample, the 2nd and 3rd harmonics were 23dB down from the 2 meter fundamental. In other words, if you are using 25 watts on 2 meters, the 2nd and 3rd harmonics had a power output of approximately 100 milliwatts: This is a power level that is comparable to a handie-talkie running on low power transmitting out-of band! We were able to get another radio of the same model and do some testing and although it was slightly "less terrible", the harmonics were still off the charts when it comes to being out of compliance with spectral purity regs, putting out several 10s of milliwatts on its 2nd and 3rd 2 meter harmonics, still more than enough to bring up a repeater. As it turns out, if you select the correct 2 meter frequency and tone, you can key up 70cm amateur mountaintop repeaters from 10s of miles away with the 3rd harmonic! There is also the 2nd harmonic to contend with: This lands in the 280 MHz area - in the middle of a frequency range that is often used for military aeromobile, among other things. If you were transmitting on 2 meters and your second harmonic happened to land on an aeromobile frequency, aircraft out to at least 100 miles line-of-sight would be able to hear your transmission! What about 222 MHz? Our samples' harmonics were about 42dB down - better than expected, but this still put it at about 2.5mW, about 20dB above the FCC rules (see FCC §97.307), worst-case, varying by about 15dB depending on the power supply voltage. A visual inspection of the radio's circuitry doesn't reveal any low-pass filtering other than that for UHF. "But there's an FCC logo on it and its specs say that it's clean?!" Yes, we noticed that and we are sure that if it was tested by the FCC (doubtful, but possible) that it probably would pass the part-15 rules in terms of incidental RF radiation from the the receiver and its onboard computer, but that testing doesn't check transmitter cleanliness. Anyway, it would cost nothing for an unscrupulous manufacturer to print whatever logos they wanted on the box or the radio. Regardless of what might be in the specs or on the box you, as a radio amateur, are ultimately responsible for making sure that your transmitters are operating properly and according to FCC regulations - not the manufacturer! Summary:
For more in-depth, technical information about this radio and its problems read this blog entry - A hilariously-bad multi-band radio. Are you operating DMR/DSTAR/Wires on 70cm and breaking the law? AMSAT, a large international organization that coordinates the operation and support of amateur radio satellites has reported that there appear to be people or groups that are operating digital modes within the 70cm satellite sub-band. It should be noted that it is illegal to operate a repeater of any type (unless it's actually in space!) in the frequency range from 435.000 to 438.000 MHz, inclusive. While it may not be illegal, it's certainly frowned-upon to do ANY sort of operation in the 435-438 MHz frequency range that is not directly related to Earth-Space operations. In other words: You should never operate on any frequency that begins with a 435, 436 or 437 unless you are trying to talk to someone via a spacecraft! It is possible that several people are using the so-called dongles or "hot spots" in this frequency range (bad idea!) and while these devices operate at very low power - a few 10s of milliwatts, it is likely that the radio being used with one of these hot-spots is not running such low power. It's worth remembering that in space, even a fraction of a watt of transmitted power can be easily detected even on a rubber duck type of antenna. AMSAT has determined that these operations are occurring in the general area of Colorado or western Midwest - but this doesn't necessarily exclude Utah. Over time they should be able to narrow down the location of these transmissions and possibly decode callsigns. If you are operating your digital radio in the 435-437 MHz area, PLEASE STOP NOW. If you are in Utah, please contact Utah VHF Society Simplex manager for advice on a frequency on which you may "safely" operate and/or refer to the page Wasatch Front Simplex frequency usage. For more information about AMSAT and other amateur satellite operations, please visit the AMSAT web page.
Things to consider if you want to put up a repeater Are you planning to put a repeater on the air for your group? Are you planning to do this along the Wasatch Front? Do you want this repeater to be on 2 meters or 70cm?If you answered yes to any of these questions, you should know the following:
What if you and your group believe that you have a need for your own repeater - Before you go too much farther down that road, consider the following:
Supporting the Idaho portion of the Intermountain Intertie The Officers of the Utah VHF Society were approached by Vance Hawley, WA7FDR, to determine if it would be possible to obtain funds from Idaho hams the same way we do in Utah to help support the Idaho portion of the Intertie repeaters. After much discussion The Utah VHF Society Officers have agreed to begin an initial effort to ask the Idaho hams who would like to support the Idaho portion of the Intertie System to join the Utah VHF Society.Any funds obtained through this effort or any donations we obtain from Idaho hams will be dedicated to Idaho Intertie System repeaters. We would like to thank all those who attended the Hamfest in Boise who made the initial effort to kick off this project by joining the Society and making generous contributions. Enough funds were raised via recent efforts to address some crucial needs, such as the purchase of new batteries for the Sawtell (West Yellowstone) repeater site and upgrade and maintenance for other projects. As more funds become available additional improvements will be made to the Idaho system. Some time down the road it may be possible for our Idaho friends to create a self supporting entity similar to the Utah VHF Society, but for now we desire to do our best to help make good things happen in Idaho! If
you want to help with this effort you may do so through the Utah VHF
Society (contact
information is here).
Any funds obtained through this effort or any
donations we obtain from Idaho hams will be dedicated to Idaho Intertie
System repeaters. Please
mark your membership and or donations for Idaho. If
anyone has any questions or suggestions please feel free to contact or
email one of the Utah VHF Society Officers.
http://utahvhfs.org For more details about each of the Idaho Repeater Linked System repeaters please click here http://utahvhfs.org/other_rpt.html#jumpoff |
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Questions, updates, or comments pertaining to this web page may be directed to: uvhfs@utahvhfs.org
