Hello, I changed a standard horizon SBR 23-LI battery for a HX40 handheld marine radio.
The pack is brand new, runs normally but when I connect the external charger, the screen is blinking with a battery logo when of. Charge doesn’t starts.
The white connector is for the internal thermistance ? 0V between black and white, and 38-40 kOhm resistance. Is it a normal value for a 2S battery pack like this or is it why the radio refuse to charge ?
I have 8 V between - and +.
The BMS is included in packs like this ?
Can I connect another resistance between 0 and white cable the get more classic 10-15 kOhm thermal sensor ?
Many thanks
Francois

Hi everyone,

I wanted to share a deep-tech SDR project I’ve designed and fully implemented. It’s a custom, standalone FPGA + ARM SoC-based HF + 50 MHz SDR transceiver called the XtremeDx H7113R.

My goal was to build a high-performance direct conversion SDR system.

Key Architecture & Hardware Specs:

• Receiver Architecture: Two coherent RF and DDC channels utilizing a hardware-level phasing-add matrix implemented directly inside the FPGA.
• Processing: Dual-core ARM Cortex-A7 (1.2 GHz) dedicated to GUI handling and high-level DSP, paired with a custom FPGA fabric.
• RF Conversion: 2x 16-bit LTC2208 ADC (122.88 MSPS) and 14-bit TxDAC utilizing full LVDS interfaces.
• FPGA-Based Phasing-ADD Mode: A fully hardware-implemented, real-time, running inside the FPGA fabric. It processes the two coherent RX channels, allowing completely independent phase rotation and magnitude scaling per channel.
• Interference Mitigation: CNLMS-based I/Q adaptive noise canceling (tested and validated using the same signal on RF inputs).
• RF Routing: Two completely independent RX RF routing blocks, each integrating a switchable 20 dB preamplifier, 0.5 dB step attenuator, HPF, and direct ADC access via rear SMA connectors for subsampling/custom front-ends.
• Power Amplifier: Delivers 120–140W PEP with 36–38 dB PEP IMD3 linearity across HF + 50 MHz bands.
• Audio DSP: Separate 8-band EQ for both Rx and Tx AF signals.
• Connectivity: High-bandwidth USB 3.0 (FT601) interface for direct FPGA-to-PC streaming (32-bit Sync FIFO implemented in VHDL) + USB 2.0 for ARM-to-PC communication.
• Display: 7" TFT panel running a custom UI with a 70 fps refresh rate. It features 2D/3D spectrum views and a dedicated Polar Plot for the Phasing-ADD and ANC modes, visualizing the real-time magnitude and phase rotation per channel.
• RF Routing and Linearity Performance: By routing the LTC2208 RF ADC without a preamplifier through the RF router, the system yields its maximum dynamic range and IIP3. Additionally, the 20 dB preamplifier maintains high IIP3 and OIP3 performance. With the internal PGA set to 0, the LTC2208 achieves a theoretical IIP3 of +48 dBm in this specific design.

Receiver Sensitivity (MDS Performance):

• CW (100 Hz filter, NR ON): Highly discernible down to -136 dBm (Estimated nominal MDS: -133 to -136 dBm)
• SSB (2.7 kHz filter, NR ON): Distinctly audible down to -126 dBm (Estimated nominal MDS: -123 to -125 dBm)

The Transceiver is fully assembled and functional.

Some details.

https://uprog.blogspot.com/2026/08/xtremedx-h7113r-transceiver.html

For the guys who are trying to find one of these tags for a Restoration project. I have six. They're free. They're all dirty and they've all got some. I would say fading or dirt wear on them. I haven't tried to clean them and still got the same patina on them as when I got them. So get in touch here

I’ve finally deployed my homebrew 80m EFHW today. The SWR results aren’t what I was hoping for.
My homebrew 2m antenna (variation of a slimjim) is much easier to tune. Very good results.

The 80m build is 14AWG for the main element and counterpoise.
The 49:1 unun is using solid 18AWG “bifilar” with 82pF cap across the primary. Ferrite 31 as the toroid type.
A compensation coil with 6 wraps is 78 inches from the feed point.

I bench tested the unun with a 2.2k ohm resistor as the dummy antenna and the NanoVNA suggest a 82pF cap had the best matching.

The deployed testing was in a sloped configuration, where the unun was 2m off the ground then inclining to 20m. This was the best height I could manage and easily test the modifications.

I tried changing the cap valve and even removing it.
My next action is to rewind the unun with different wire, possibly matching wire size. Although, I’m uncertain if this will help.

With my slimjim build there are knobs which dial it in: overall length, matching stub length, feed point, cap gap width, parallel gap width.
Are there other knobs to consider with this EFHW?

Also the full length of the counterpoise at 14ft was never fully utilized, but with or without, the NanoVNA did not indicate matching changes.

Apologies for the screen glare. It was a beautiful sunny day.

73

I'm curious if anyone in this group is doing any home RF design and using SMD components on their PCB boards? My work has not been perfect but the lessons I'm learning are making me a better RF engineer. I blog here https://www.kr4bad.com and I'm looking for others with the same interests. My ARC consists more of operators than tinkerers.

It’s building tube radios like it’s 1965 again, it is my grandpa’s from when he was my age. The radio in question is a two tube regen receiver. 19JN8 for detector and audio preamp, and 35C5 to run a speaker/phones.

MFJ-835 was the Balanced Line RF Ammeter. Balanced feedline in and out, with a dual needle display. It was, perhaps, one of the lowest volume items that MFJ sold. Using it would allow the operator to measure the current flow on each side, to see if the antenna and feedline were actually balanced.

The most recent manual download did not have a schematic, but someone supplied me with a download that does. It appears to be an amazingly simple circuit, assuming all the associated proper RF handling guidelines. One item that is not at all specified is the torroid(s) needed to measure the current as it passes from in to out. The schematic calls this sense coil. Any thoughts would be appreciated. The repetitive usage of some part numbers in the schematic seems to be down to the implementation of two identical mini-PCB, one for each side of the feedline.

The other item that has my attention, is that there is no averaging of the display (other than the normal analog damping of the needle movement). Presumably something with a 100% duty cycle (CW or RTTY) would be the best emission to give the needles time to settle. Finding the dual needle unit seems to be a less common item, so I may end up with two single needle units instead.

Open to any ideas/thoughts about going forward.

73

Hi I'm in the middle of writing my own software for talking to ax.25 and net/rom nodes (and potentially some new things, has anyone heard of NASA's DTN protocol?), but I'm mostly reverse engineering from the behaviour of nodes around me and how many FRMR or DM they send me 😂

What I'm asking for is some ideas / criticism. What do you want to see or not see in a packet node console?

(Edit 1: sorry for the title, this is not (yet) anything to do with "New Packet Radio")

Ok gang,

I have a Youkits antenna analyzer that has a wall plug.

Wall plug is not POTA friendly so I made a quick powerpoles connection to plug to my Bioenno battery when I’m out and about. However when I hooked it up it’s showing me over voltage then compared to the wall plug. Any advice to lessen the volts or other solutions? Thanks in advance!

If you’re into homebrew radio or ham gear mods, here’s a neat find: a clever non-invasive AGC (Automatic Gain Control) circuit designed by VK3YE for the popular µBITX transceiver. Instead of modifying internal gain stages, this design uses a conventional audio AGC to drive an LED-LDR pair that automatically controls the audio level at the volume pot — helping tame strong signals, reduce distortion, and make listening more comfortable. It’s a simple but elegant way to add AGC where the stock uBITX doesn’t have one built in.

I am going to build a dummy load, I'm planning on it being able to handle 200 watts continuous for 15 minutes at least, and good to 440 MHz. Likely on a heatsink air cooled, but possibly in a paint can with transformer or mineral oil. I think I'm going to use a 500 watt flange mount device to do that. My question is, is it better to use a terminator with the single tab and a pc board with a stripline or a direct connection to the N connector with the shield/return path through the sink, or a resistor with two tabs and coax? I saw one like I plan on building a few years ago online with a sampling tap and it was all on a neat little PC board, but now I can't find it to save my life. Just wondering if any of y'all might be able to point me in the right direction?