The RX-888 (Mk2) and external clocking Figure 1:  Modified RX-888(Mk2) Note: I have posted blog two previous entries related to the RX-888 (Mk2) that you may find relevant: Improving the thermal management of the RX-888 (Mk2) - link - This page talks about highly recommended modifications to the RX-888 to reduce internal heat to improve reliability. Measuring signal dynamics of the RX-888 (Mk2) - link - This is a discussion of how much (and little) signal is needed to stay within the dynamic range of the RX-888 and the effects of gain and attenuator settings. Adding an extern ..read more

Recently, a Kenwood TS-850S - a radio from the mid-early 1990s - crossed my workbench.  While I'm not in the "repair business", I do fix my own radios, those of close friends, and occasionally those of acquaintances:  I've known this person for many years and have many mutual friends. If you are familiar with the Kenwood TS-850S to any degree, you'll also know that they suffer from an ailment that has struck down many pieces of electronic gear from that same era:  Capacitor Plague. Figure 1: The ailing TS-850S.  The display is normal - except for the frequency display ..read more

One of the (many) banes of the amateur radio operator's existence is often found at the end of an Ethernet cable - specifically a device that is being powered via "Ethernet":  It is often the case that interference - from HF through UHF - emanates from such devices. Figure 1: POE camera with both snap-on ferrites installed - including one as close to the camera as possible - and other snap-on/toroids to suppress HF through VHF. Click on the image for a larger version. Why this happens Ethernet by itself is usually relatively quiet from an (HF) RF standpoint:  The base freque ..read more

It is likely that - almost no matter where you were - you were aware that a solar eclipse occurred in the Western U.S. in the middle of October, 2023.  Wanting to go somewhere away from the crowds - but along the middle of the eclipse path - we went to an area in remote west-central Utah in the little-known Conger Mountains. Clint, KA7OEI operating CW in K-6085 with Conger mountain and the JPC-7 loaded dipole in the background. Click on the image for a larger version. Having lived in Utah most of my life, I hadn't even heard of this mountain range even through I knew of the sever ..read more

Note: This is a follow-up to a Part 1 blog post on this topic where we discuss in general how "rotating" (or switched) antennas may be used to determine the apparent bearing of a transmitter.  It is recommended that you read Part 1 FIRST and you can find it at:  "'TDOA' direction finder systems - Part 1 - how they work, and a few examples." - LINK. In part 1 (linked above) we discussed a simple two-element "TDOA" (Time Difference Of Arrival) system for determining the bearing to a transmitter.  This method takes advantage of the fact that - under normal conditions - one can pres ..read more

In a previous post I discussed how a band-pass "cavity" could be constructed from a chunk of 1-5/8" Heliax (tm) cable (a link to that article is here).  This is the follow-up to that article. Figure 1: The dual notch filter assembly - installed at the repeater.Click on the image for a larger version. Notch versus band-pass As the name implies, a "notch" cavity (or filter) removes only a specific frequency, ideally leaving all others unaffected while a "band pass" cavity does the opposite - it passes only a specific frequency.  Being the real world, neither type of filter is ..read more

Figure 1: The JPC-7 and its original set of components in the case.  On the left is a zippered section with the balun, strap, feedpoint and mounting hardware for the elements.  On the right can be seen the two telescoping sections, the two loading coils and the four screw-together mast sections. Click on the image for a larger version. The JPC-7 (apparently by BD7JPC) is a portable dipole antenna - somewhat similar to the "Buddipole" - in that it is tripod-mounted, with telescoping elements that can be oriented horizontally.  Both use loading coils to increase the elect ..read more

It should not have escaped your attention - at least if you live in North America - there there are/have been two significant solar eclipses occurring in recent/near times:  One that occurred on October 14, 2023 and another eclipse in April, 2024.  The path of "totality" of the October eclipse happened to pass through Utah (where I live) so it is no surprise that I went out of my way to see it - just as I did back in 2012:  You can read my blog entry about that here.  Figure 1: The eclipse in progress - a few minutes before "annularity". (Photo by C. L. Turner) I w ..read more

As I am wont to do, I recently spent a week camping in the "Needles" district of Canyonlands National Park.  To be sure, this was a bit closer to "glamping" in the sense that we had a tent, a flush-toilet a few hundred feet away, plenty of food, solar panels for power and didn't need to haul our gear in on our backs - at least not any farther than between the vehicle(s) and the campsite. While I did hike 10s of miles during the week, I didn't hike every day - and that left a bit of "down time" to relax and enjoy the local scenery. As a first for me - even though I have camped there many t ..read more

Fig 1: The Hammond 1590 aluminum case housing the FE-5860A rubidium osc- oscillator and other circuitry - the markings faded by time and heat. Click on the image for a larger version. Recently I was getting ready for the October 14, 2023 eclipse, so I pulled out my two 10 MHz rubidium frequency references (doesn't everyone have at least one?) as I would need an accurate and (especially) stable frequency reference for transmitting:  The details of what, why and how will be discussed in a post to be added in the near future. The first of these - my Efratom LP-101 - fired up just fi ..read more