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Audio Upgrade Kit
Kiwa offers the Audio Upgrade as described below in kit form. Full installation instructions are included.
Audio Upgrade kit $35.00
Shipping and Handling within North America $3.00
Shipping and handling outside North America $5.00

Ultimate Rejection Filter Upgrade Kit
Kiwa offers the Ultimate Rejection Filter Upgrade as described below in kit form. Full installation instructions are included.
Ultimate Rejection Filter Upgrade Kit $30.00
Shipping and Handling within North America $2.00
Shipping and Handling outside North America $4.00

Ultimate Rejection Inductor Upgrade Kit
Kiwa offers the Ultimate Rejection Inductor Upgrade as described below in kit form. Full installation instructions are included.
NRD535 Ultimate Rejection Inductor Upgrade Kit $15.00
NOTE: Shipping and Handling is the same as the Ultimate Rejection Filter upgrade. Only one shipping charge is required for both the Filter and Inductor upgrades.

Filter Kits
Kiwa offers the Premium Filter Module for the AUX filter slot. Please NOTE: we are currently out of stock of narrow filters. The only available bandwidths are 6.5 to 10.0 kHz. Installation instructions are included - soldering is required.
Premium Filter Module $75.00
Shipping and Handling $6.00 (North America)
Shipping and Handling outside North America $7.00

AGC Modification
The AGC modification will speed up the attack and decay of the AGC when listening in AM mode. Installation instructions are included - soldering is required. AGC Mod $5.00 (includes shipping in North America)
Shipping and Handling outside North America $3.00

Kiwa Upgrades
The following is available by sending the receiver to Kiwa Electronics.

Audio Upgrade
This modification is for those who wish to have the best audio quality the set has to offer. We replace all of the capacitors in the audio path, which includes the ECSS board, the IF Board and the Audio Power Amplifier circuitry. Nearly 50 capacitors are replaced with types which will improve the audio clarity and intelligibility. The capacitors that normally bypass the audio DC rails are also replaced with types that will improve the audio clarity The end result is a receiver that provides an improvement in intelligibility that will make listening more enjoyable with less listening fatigue.
Audio Upgrade $80.00

For more information regarding Kiwa Audio Upgrades - please see Kiwa Audio Upgrades - A Brief History

Sync Detector Lock
This modification will improve the locking performance of the ECSS Sync Detector under severe fading and weak signal conditions.
Sync Detector Upgrade $30.0

Ultimate Rejection Filter Upgrade
This modification will improve the Ultimate Rejection or Ultimate Selectivity of the IF Filter Board. Replacement of FL2 on the IF Filter Board will sharpen the filter slopes of the other filter bandwidths from the -70 dB to -100 dB range. The stock filter has a 12 kHz bandwidth with an ultimate rejection of 40 dB. The replacement filter has a bandwidth of 8 kHz with an ultimate rejection of 65 to 70 dB.
Ulitmate Rejection Upgrade $40.00

Ultimate Rejection Inductor Upgrade
This modification like the Filter upgrade above will improve the Ultimate Selectivity of the IF Filter Board. The orignal inductors used to select the individual 455 kHz filters have considerable leakage or radiation. This prevents the filters from performing optimally. The Kiwa Ultimate Rejection Inductor Upgrade replaces all the inductors with magnetically shielded SMD (surface mount) Inductors. The shielded inductors are guaranteed not to reradiate. (Note: the only leakage that could occur is from the extremely short lead lengths.) An additional benefit to this upgrade is that the inductors are mounted on the solder side of the board where an extensive ground-plane provides additional shielding from the component side. This upgrade is superior to other methods that use resistors since there is not the signal loss inherent with series resistors in the signal path.
Ultimate Rejection Inductor Upgrade $25.00

Audio Tone Tilt
The Tone control in the NRD 535 is basically ineffective especially if using the narrow bandwidths.
Kiwa has developed a tone control that is unique to communications receivers called a Tone Tilt. The end result is a tone control that is very effective not only for the wider bandwidths but also for bandwidths as narrow as the stock SSB bandwidth.
The concept is rather simple. Imagine a flat frequency response when the tone control is at the center position. When the control is adjusted to the right or clock-wise position the high frequencies are boosted and the low frequencies are reduced. Likewise when the control is adjusted to the opposite position, the reverse is created - or the high frequencies are attenuated and the low frequencies are boosted. The tonal variation is over 20 dB compared to the stock tone control that has 6 dB variation.
The Tone Tilt is like a Teeter-Totter like platform that is centered at 700 Hz. Tonal variations will tilt the platform accordingly. The end result is a tone control that has very little coloration (changing one end of the audio spectrum without change to the other end). The Tone Tilt is similar in design to the Tone Tilt once used in the Kiwa MAP unit (now discontinued).
Audio Tone Tilt $60.00

Gilfer Switch Mod
This mod is identical to the mod once offered by Gilfer Shortwave.It basically creates two bandwidths using the AUX filter slot. A switch is mounted on the rear panel that allows the AUX Filter position to be enabled. For example, a PFM filter module is installed at the AUX filter position. With the AUX Filter switch ON, the PFM filter module is enabled. Turning the AUX Filter switch OFF disables the PFM and the AUX filter position will default to the bandwidth of FL2. If FL2 is the stock filter, the bandwidth would be 12.5 kHz. If the Ultimate Rejection Upgrade has been performed, the bandwidth would be 8.2 kHz.
Gilfer Switch Mod $35.00

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