The JPC-12 antenna (possibly made by BD7JPC) is relatively inexpensive a portable vertical antenna - made in China, of course - that may be found for sale at quite a few places  under a few different brand names (including "Chelegance") with the price varying very widely - sometimes well over $200 - but I got mine via AliExpress for about $120, shipped, about a year and a half ago. Note:  I analyzed the JPC-7 loaded dipole antenna - which is made by the same company and uses many of the same components - and reported on it in previous article, and you may find that discussion HERE ..read more

On this blog I have posted three previous entries related to the RX-888 (Mk2) which may be of interest to the reader: Figure 1 - The (stock) RX-888 Using an external clock with the RX-888 (Mk2) - link  - On this page we detail the sort of signals that it takes to clock an RX-888 from an external source. 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 lit ..read more

Comment: This article - while it centers about the investigation of a SolarEdge PV (PhotoVoltaic) system - the discussions of techniques and strategies should be generally useful when investigating interference from any make or model of PV system - or even interference from other sources. * * * Several months ago I got a call from a local amateur who was very concerned about a sudden rise in his noise floor across the HF spectrum (3-30 MHz).  This increase in noise seemed to be coincident with the installation and commission of a 5 kW PV (Photovoltaic, or "Solar") electrical system on the ..read more

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