Online calculator of ferrite material permeability interpolations

Many of my articles call for finding the complex permeability of a ferrite components from manufacturer’s data.

Let’s explore an example used in a recent article, Another small broadband RF transformer using medium µ ferrite core for receiving use – 50:450Ω.

The core used was a Fair-rite ferrite core of #43 material, and the magnetising impedance of a 5t winding needed to be found.

Above is a chart from Fair-rite’s catalog. Permeability is a complex quantity and is frequency dependent. One could scale from the graph, the values for µ’ and µ” at the frequency of interest. Continue reading Online calculator of ferrite material permeability interpolations

Another small broadband RF transformer using medium µ ferrite core for receiving use – 50:450Ω

A simplified design for small broadband RF transformers using medium µ ferrite core for receiving use. The specific application is an impedance transformer for a nominally 450Ω antenna to a 50Ω receiver input. Intended frequency range is from 0.5 to 15MHz.

The characteristic of typical medium µ ferrite mixes, particularly NiZn, are well suited to this application.

This article continues with the design discussed at BN43-2402 balun example, but using a BN43-202 with 5t primary and 15t secondary for a nominal 1:9 50:450Ω transformer (though at high ratios, the transformation is only nominal).

Lets consider a couple of simple starting points for low end and high end rolloff. Continue reading Another small broadband RF transformer using medium µ ferrite core for receiving use – 50:450Ω

Another small broadband RF transformer using medium µ ferrite core for receiving use – 50:3200Ω

A simplified design for small broadband RF transformers using medium µ ferrite core for receiving use. The specific application is an input transformer to a nominally 2kΩ receiver at around 9MHz (a panadapter).

The characteristic of typical medium µ ferrite mixes, particularly NiZn, are well suited to this application.

This article continues with the design discussed at BN43-2402 balun example, but using a 2t primary and 16t secondary for a nominal 1:64 50:3400Ω transformer (though at high ratios, the transformation is only nominal).

Lets consider a couple of simple starting points for low end and high end rolloff. Continue reading Another small broadband RF transformer using medium µ ferrite core for receiving use – 50:3200Ω

Implementation of G5RV inverted V using high strength aluminium MIG wire – 12 month review

This article continues on from Implementation of G5RV inverted V using high strength aluminium MIG wire documenting review after 12 months operation under a wide range of temperature, humidity and wind conditions.

Above is a view of the steel mast with the Inverted V G5RV rigged from the top of the 11m mast using a halyard though a purchase on a small gibbet to offset the antenna and feed line from the mast. There are lateral guys at 7m height, and the left hand one is non-conductive synthetic fibre rope. Atop the mast is a 2m/70cm vertical. Continue reading Implementation of G5RV inverted V using high strength aluminium MIG wire – 12 month review

Anytone AT-D868UV: initial impressions

This article reports initial impressions of an Anytone AT-D868UV hand held VHF/UHF dual mode (DMR/FM) radio.

Above, the AT-D868UV, purchased for about A$225 incl post from Hong Kong. This model had a GPS though that is unusable on ham DMR networks, so it is wasted money if you like. They may be more expensive through online shops that collect GST, and of course in countries where tariffs are applied to make them great again, prices may be higher.
Continue reading Anytone AT-D868UV: initial impressions

Pulsar V233-0060 stripped down

I bought a cheap Pulsar V233-0060 on eBay, you know, one that was advertised as “was working 10 years ago, just needs a battery”.

Of course if that was true, the seller would fit the battery and describe it as working and get lots more money for it.

Pulsar is one of Seiko’s brands, and this movement appears in Seiko branded watches.

Anyway, as it inevitably the case, it did not work.

External examination revealed that with a good battery, the 32kHz crystal was running, but no motor pulses. A further test with external turbo magnetic drive showed the motion works was working… so now pointing to a coil problem.
Continue reading Pulsar V233-0060 stripped down

40m filter for WSPRlite flex

The WSPRlite flex requires external low pass filters for each band of operation.

Since my experiments will be conducted on the 40m band, the following low pass filter meets the requirement. The inductors and capacitors make a seven element Chebyshev filter as designed by G3CWI for use in a 50Ω system.

Implementation

Above, the filter is assembled on a piece of matrix board with two BNC connectors. The inductors are fixed with hot melt adhesive, and the whole thing served over with heatshrink tube. It is not waterproof. Continue reading 40m filter for WSPRlite flex

Another RFI mod of a speaker mic for DMR use

I bought a remote speaker-microphone (RSM) for a DMR portable from eBay (~$12 posted). Experience says that these suffer RF ingress which is seriously bad in DMR due to the amplitude modulation of the transmitted signal.

This RSM had somewhat improved filtering around the electret compared to others I have purchased. Continue reading Another RFI mod of a speaker mic for DMR use

WSPR for A/B tests – a discussion – part 4

Continuing from WSPR for A/B tests – a discussion – part 3.

Regression techniques

Another technique for exploring the relationship between pair variable is a regression model. In the case of these experiments, a simple model that is a good candidate is that SNR_B=m*SNR_A+b, a simple linear regression. A simple  solution is to find m and b to minimise the sum of squares of errors between the predicted SNR_B and measured SNR_B.

Above is a frequency distribution of data extracted from a month studied in 2011. There are almost half a million spots on 40m contributing to this analysis, so it covers a wide range of propagation conditions during the month, and includes all stations spotted by all stations. Continue reading WSPR for A/B tests – a discussion – part 4