Comparison

iSDR vs Ham Radio Prep

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

iSDR

This app allows experimenters and amateur radio enthusiasts to build a portable software-defined radio receiver using their iOS device. It processes radio signals using the device's processor and offers various display and filtering modes. Additional hardware is required for live signal reception.

Highlights
  • Six receive mode settings (USB, LSB, CW, AM, FM, Binaural)
  • Selectable bandwidth settings
  • 120 dB dynamic range signal strength meter
  • Three AGC settings (fast, slow, off)
  • Spectrum, Waterfall, and Oscilloscope display modes
  • Supports downloaded audio-format spectrum files via iTunes
  • Embed center frequency in file names for automatic display
Features
Read full description

PLEASE READ THE ENTIRE DESCRIPTION BEFORE PURCHASING. iSDR is the first and only software-defined radio application compatible with the Apple iPhone®, iPod touch® and iPad™. iSDR is for experimenters and amateur radio enthusiasts looking to construct a truly portable software-defined radio receiver. Additional hardware is required to receive live signals. Currently, iOS devices will not work with RTL-SDR USB dongles, and they are not supported by iSDR. PLEASE NOTE: Receiving live on-air signals using iSDR requires purchasing or constructing a "quadrature sampling detector (QSD)" RF front-end device, and connecting it between an antenna and the microphone input jack. Alternatively, iSDR can be used to implement a panadapter for use with a compatible radio receiver. Without a QSD RF front-end or a connected radio, iSDR will only play I/Q recordings of actual radio signals. Additional recordings can be loaded into the app using iTunes file sharing - some recordings are available free to download from the Internet. Visit the support web site for more information. iSDR includes a sample I/Q recording featuring 30 seconds of a ham radio contest. This is for demonstration purposes only. It is not meant to fool you! It is to allow you to experience how the app works without having to do anything yourself: just turn it on. You can download and play your own files if you like. Please see the support page for details. AND PLEASE contact us directly if you experience any issues with using this app. We will respond promptly when provided with details. When iSDR is used to receive live radio signals, receiver performance will depend largely on the quadrature sampling detector and antenna that you use. iSDR is a software-defined receiver application for use on mobile handset devices and iPad. Despite its extreme portability, the app utilizes the same digital signal processing techniques found in PC-based SDR receivers. It does frequency domain filtering using a theoretical "brick wall" sinc filter algorithm to provide steep and deep bandpass filtering. iSDR doesn't utilize any DSP hardware but instead uses the iOS device's processor to implement DSP algorithms. Features o Six receive mode settings: USB, LSB, CW, AM, FM* and Binaural. o Selectable bandwidth settings for each mode. o Signal strength meter covering 120 dB of dynamic range with peak and average power indication. o Three AGC settings: fast, slow, and off. o Three display modes: Spectrum, Waterfall and Oscilloscope. o File sharing** supports downloaded audio-format spectrum files synced using iTunes. o Most PCM file formats are supported, including .wav and .caf. o Embed the center frequency in your file names and iSDR will automatically display the correct frequency! o Tune quickly using a single touch to the display screen, or tune precisely using the rainbow tune bar. o Change radio settings with a simple double-tap action to the red cursor, mode text, AGC indicator or signal grid! o Up to 44.1 kHz of available spectrum bandwidth. o Dimmable semi-log or linear spectrum grid (native Settings app only). o Adjustable CW offset (native Settings app only). o Monaural microphone input automatically adjusts the display to 22 kHz bandwidth. o Automatically detects if external audio is available for receiving live signals (menu selectable). o Reverse I/Q stereo input logic (menu selectable). *FM mode is not supported for monaural signals, and will not appear as a mode selection unless stereo audio (live or recorded) is available. Narrowband FM only: 16 kHz or 11.2 kHz bandwidth. Please contact Digital Confections with your questions and suggestions!

About

Ham Radio Prep

Prepare for your ham radio license exams with comprehensive study materials. Access video lessons, track your progress, and take practice tests designed to mirror the official FCC exams for all three license levels.

Highlights
  • Covers all 3 license levels
  • Premium video lessons
  • Progress tracking per lesson
  • FCC-style practice tests
  • Exam readiness dashboards
Features
Read full description

The fastest, easiest, and most informative way to get your ham radio license. > Includes all 3 Levels: Technician License, General License, and Amateur Extra License > Learn the material with premium video lessons > Track Your Progress For Each Lesson / Subpool > Practice Tests Built Using the Subpools Just Like the Real FCC Exam > Dashboards to Track Exam Readiness See why thousands of students have chosen HamRadioPrep.com to effectively study for their amateur radio license exams.

Screenshots

iSDR4 screens
Ham Radio Prep4 screens

Verdict

The call

The clearest difference is price: Ham Radio Prep at Free against iSDR's $0.99. Ham Radio Prep also leads on rating (4.8 vs 2.5) and review sentiment (80% vs 52%). iSDR's advantage is iOS requirement (9.0 vs 15.1). On ads, in-app purchases and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Ham Radio Prep is free to download; iSDR costs $0.99 up front. iSDR sells 1 one-off in-app purchase and Ham Radio Prep sells 4 one-off in-app purchases. Whichever you choose, the download price is not the number that matters.

ReceptionRating · Positive reviews · Number of ratings

Ham Radio Prep holds the better App Store score, 4.8 against 2.5. That said, the two scores are not equally well evidenced: Ham Radio Prep has 2.2K ratings behind it against 11, so its average is the more settled of the two. Written reviews point the same way: 52% of iSDR's written reviews are positive against 80% of Ham Radio Prep's.

UpkeepUpdate frequency

iSDR ships an update every 3 months, Ham Radio Prep every 2 weeks. The most recent releases landed on October 26, 2026 and October 29, 2026 respectively.

Scorecard7 real differences · 3 level
iSDR versus Ham Radio Prep: the parameters behind the verdict, then further details
ParameteriSDRHam Radio Prep
Price$0.99Free — better
Rating2.5 (11 ratings)4.8 (2.2K ratings) — better
Positive reviews51.7% of reviews79.6% of reviews — better
Number of ratings112.2K — better
Update frequencyEvery 3 monthsEvery 2 weeks — better
AdsNoNo
In-app purchasesYesYes
MonetizationPaidFree with in-app purchases — better
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS9.0 — better15.1
Further details — not scored
Size36 MB53 MB
Age rating4+4+
DeveloperDigital Confections LLCWorld Radio League Inc.

Customer experience

iSDR

All ratings11 ratings
Positive36.4%
Neutral0.0%
Negative63.6%
Written reviews58 reviews
Positive51.7%
Neutral12.1%
Negative36.2%

Ham Radio Prep

All ratings2,181 ratings
Positive95.6%
Neutral1.1%
Negative3.2%
Written reviews196 reviews
Positive79.6%
Neutral5.1%
Negative15.3%

Bugs and requests

iSDR

Not enough reviews yet to summarise bugs or requests.

Ham Radio Prep

Reported bugs

3 issues
  • Lessons locked after initial free content
  • Advertisements causing app to freeze
  • Progress not tracking across platforms

Requested features

3 requests
  • Online proctoring for exams
  • Improved sync between app and website
  • More practice questions and tests

In-app purchases

1 purchases

iSDR

One-time1
  • Wi-Fi Radio ControlFree
4 purchases

Ham Radio Prep

One-time4
  • Technician License Exam Course$34.99
  • In-App Video Bundle$49.99
  • General + Technician Course$55.00
Show 1 more
  • Full Course Access, All Levels$79.99

Questions

Is iSDR free?
iSDR costs $0.99, and also offers in-app purchases.
Is Ham Radio Prep free?
Ham Radio Prep is free to download, with in-app purchases available.
Which has better reviews, iSDR or Ham Radio Prep?
Ham Radio Prep is rated higher. iSDR averages 2.5 out of 5 from 11 ratings, while Ham Radio Prep averages 4.8 from 2.2K ratings.
Do iSDR or Ham Radio Prep have ads?
Neither iSDR nor Ham Radio Prep shows ads.
Which is updated more often, iSDR or Ham Radio Prep?
iSDR ships an update every 3 months, and Ham Radio Prep every 2 weeks. Most recently, iSDR was updated on October 26, 2026 and Ham Radio Prep on October 29, 2026.

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