Comparing sensitivity figures of an AM receiver and SSB receiver

Receiver sensitivity is commonly given as some signal level, say in µV, for a given Signal to Noise ratio (S/N), say 10dB. For AM, the depth of sinusoidal modulation is also given, and it is usually 30%. In fact these are power ratios in the context of and some nominal reference receiver input impedance.

In fact what is commonly measured is Signal + Noise to Noise ratio, and of course this ratio is one of powers. For this reason, specifications often give (S+N)/N.

This article discusses those metrics in the context of ‘conventional’ receivers and introduces the key role of assumed bandwidth through the concept of Equivalent Noise Bandwidth..

Let’s consider the raw S/N ratio of an ideal AM detector and ideal SSB detector.

Raw Signal/Noise

AM

 

Above is a diagram of the various vector components of an AM signal with random noise, shown at the ‘instant’ of a modulation ‘valley’. The black vector represents the carrier (1V), the two blue vectors are counter rotating vectors of each of the sideband components, in this case with modulation depth 30%, and the red vector is 0.095V of random noise rotating on the end of the carrier + sideband components. Continue reading Comparing sensitivity figures of an AM receiver and SSB receiver

Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2×2631540002 – measurement of Zcm

Low power Guanella 1:1 balun with low Insertion VSWR using a pair of Fair-rite 2631540002 suppression sleeves – design workup presented a desk design of a low power balun. This article presents measurement of common mode impedance Zcm of a prototype using a nanoVNA.

Above is the prototype 2631540002×2 wound with 3.5t of RG316. Continue reading Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2×2631540002 – measurement of Zcm

Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2843009902 binocular – measurement of Zcm

Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2843009902 binocular – design workup presented a desk design of a low power balun. This article presents measurement of common mode impedance Zcm of a prototype using a nanoVNA.

Above is the prototype 2843009902 binocular wound with 3.5t of RG316. Continue reading Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2843009902 binocular – measurement of Zcm

Baofeng BF-F8HP battery and charging experience

The Baofeng BF-F8HP is a U/V portable FM transceiver. The battery supplied is labelled BL-5 and rated at 2800mAh.

Of course it is supplied with a Chinese power supply that does not comply with Australian Standards, and is illegal to sell in Australia, even second hand by a non-business seller.

It seems common that Baofeng portables use a charger cradle that is powered from nominally 10VDC. The question arises as to the maximum input voltage. Continue reading Baofeng BF-F8HP battery and charging experience

Baofeng GT-5TP battery and charging experience

The Baofeng GT-5TP appears to be a UV-82 derivative… there are many such derivatives. The battery supplied is labelled BL-8 and rated at 2000mAh. It seems that Baofeng makes two incompatible batteries labelled BL-8, a slightly different (but incompatible) BL-8 battery is used on the UV-82.

Of course it is supplied with a Chinese power supply that does not comply with Australian Standards, and is illegal to sell in Australia, even second hand by an end user.

It seems common that Baofeng portables use a charger cradle that is powered from nominally 10VDC. The question arises as to the maximum input voltage. Continue reading Baofeng GT-5TP battery and charging experience

Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2843009902 binocular – design workup

The article Low power Guanella 1:1 balun with low Insertion VSWR using a pair of Jaycar LF1260 suppression sleeves describes a current balun with low Insertion VSWR for operation at modest power levels. The design was based on Jaycar LF1260 cores which are readily available in Australia.

This article presents the workup of a balun with similar design objectives using a low cost Fair-rite 2843009902 binocular core (BN43-7051).

Above, a pic of the core. Continue reading Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2843009902 binocular – design workup

Review of MXITA SMA-8 #2

The MXITA SMA-8 is a low cost torque wrench for 8mm, specifically for SMA connectors. It has an adjustable calibration, supplied at 1Nm but easily adjusted down to 0.6Nm to suit common brass SMA connectors, especially of doubtful quality.

I bought this after seeing several recommendations on a nanoVNA forum.

Above is the factory pic of the SMA-8. Continue reading Review of MXITA SMA-8 #2

Return Loss Bridge – some woolly thinking – a Simsmith model of a reflection bridge

Return Loss Bridge – some woolly thinking discussed some online opinions on the practical measurement range of nanoVNA, and underlying reasons… but both were flawed.

Reflection Bridge and Return Loss Bridge are somewhat synonymous, in practice to measure Return Loss one is interested in the magnitude of the response, and to measure the complex reflection coefficient or s11, both magnitude and phase are of interest.

He derives a flawed expression for bridge response, then plots a dodged up version to demonstrate the asymmetry of the response.

Above is Oristopo’s graph. Continue reading Return Loss Bridge – some woolly thinking – a Simsmith model of a reflection bridge

Return Loss Bridge – some woolly thinking

Some discussion on groups.io nanovna-users attempts to explain the behavior of the RF Return Loss Bridge used in some VNAs and other instruments, proof if you will that the instruments are not capable of measuring more than a few hundred ohms.

Oristopo gives a diagram and explanation.

Above is his diagram. He gives an expression that he states applies when R1=R3=R4=Rm: im = sqrt(Vf*(Rm – R2)/(12*Rm + 4*R2)). Continue reading Return Loss Bridge – some woolly thinking

Low power Guanella 1:1 balun with low Insertion VSWR using a pair of Fair-rite 2631540002 suppression sleeves – design workup

The article Low power Guanella 1:1 balun with low Insertion VSWR using a pair of Jaycar LF1260 suppression sleeves describes a current balun with low Insertion VSWR for operation at modest power levels. The design was based on Jaycar LF1260 cores which are readily available in Australia.

This article presents the workup of a balun with similar design objectives using a pair of low cost Fair-rite 2631540002 cores (FB-31-5621) which are similar in size to the LF1260 and have higher µi (1500 vs 1000).

Above, a pic of the cores from Amidon’s catalogue. Continue reading Low power Guanella 1:1 balun with low Insertion VSWR using a pair of Fair-rite 2631540002 suppression sleeves – design workup